# CHEM 1111 ACC Flame Tests and Atomic Emission Spectra Lab Report

Austin  Community  College  CHEM  1111  –  General  Chemistry  I  Lab
Experiment  1
Measurements

LEARNING  OBJECTIVES

Measure  mass  accurately  using  an  analytical  balance
Measure  volume  of  a  liquid  using  various  types  of  glassware
Operate  a  pipet  and  a  pipet  bulb
Read  a  meniscus  correctly
Measure  temperature  using  a  thermometer
Understand  relationships  between  mass,  volume  and  density
Calculate  absolute  error  and  percent  error  for  a  measured  quantity
Apply  rules  for  significant  figures  in  calculations

INTRODUCTION
Every   measurement   has   error   associated   with   it.     Error   is   defined   to   be   the   difference
between   a   measured   (or   calculated)   value   and   the   actual   (or   accepted)   value.     In   this
experiment,   we   will   examine   the   error   associated   with   the   use   of   some   common   chemistry
glassware:   a   beaker,   a   graduated   cylinder,   a   volumetric   flask   and   a   volumetric   pipet
(Figure  1-­‐1).

Figure  1-­‐1:    Glassware  to  be  examined  in  this  experiment

We  will  consider  two  cases.    First,  we  will  answer  the  question:  Which  piece  of  glassware
more   accurately   contains   a   reported   volume   of   liquid?     Second,   we   will   answer:   Which
piece  of  glassware  more  accurately  delivers  a  reported  volume  of  liquid?
To   answer   the   first   question,   we   will   compare   a   150   mL   beaker,   a   100   mL   graduated
cylinder  and  a  100  mL  volumetric  flask.    As  accurately  as  possible,  we  will  measure  100  mL
of  water  using  each  piece  of  glassware.    Because  the  density  of  water  is  well  known,  we  can
1-­‐1
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
use  the  mass  of  water  along  with  its  density  to  calculate  the  volume  of  water  contained  in
each  piece  of  glassware.
To  answer  the  second  question,  we  will  compare  a  10  mL  graduated  cylinder  and  a  10  mL
volumetric   pipette.     Here,   we   will   measure   10   mL   of   water   as   accurately   as   possible,   and
then   transfer   the   water   into   a   pre-­‐weighed   beaker.   As   before,   the   mass   of   water   along   with
its   density   will   be   used   to   calculate   the   volume   of   water   delivered   by   each   piece   of
glassware.

PROCEDURE

Part  1:    Which  piece  of  glassware  most  accurately  contains  a  stated  volume?
Measure  and  record  the  mass  of  a  150  mL  beaker,  a  100  mL  graduated  cylinder  and  a  100  mL
volumetric  flask.    Make  sure  that  all  glassware  is  clean  and  dry  before  measuring  the  mass.
Be  sure  to  record  the  entire  mass  given  by  the  balance  (i.e.  record  all  of  the  digits  displayed;
DO  NOT  ROUND,  even  if  the  last  digit  is  a  zero).
Fill  each  piece  of  glassware  with  100  mL  of  water  as  accurately  as  possible.    A  transfer  pipet
should   be   used   to   carefully   adjust   the   volume   of   water   in   each   piece   of   glassware.     When
water  is  placed  in  a  glass  container  the  surface  of  the  water  forms  a  curved  surface  called  a
meniscus.     The   volume   of   water   should   be   determined   by   looking   at   the   bottom   of   the
meniscus  (Figure  1-­‐2).

Figure  1-­‐2:    Reading  a  meniscus

Measure  and  record  the  mass  of  each  piece  of  glassware  containing  water.    Once  again,  bee
sure   to   record   the   entire   mass   displayed   –   DO   NOT   ROUND.     Use   a   thermometer   to   measure
the  temperature  of  the  water  in  each  container  to  the  nearest  degree.

Part  2:    Which  piece  of  glassware  most  accurately  delivers  a  stated  volume?
Measure   and   record   the   mass   of   a   clean,   dry   150   mL   beaker.     As   accurately   as   possible,
measure   10   mL   of   water   into   a   10   mL   graduated   cylinder.     [Note:     It   is   not   necessary   to
measure   the   mass   of   the   empty   graduated   cylinder.]     Pour   the   water   from   the   graduated
cylinder  into  the  pre-­‐weighed  beaker.    An  aliquot  is  defined  to  be  a  small  portion  of  a  total
amount   of   liquid.     The   water   transferred   from   the   graduated   cylinder   to   the   pre-­‐weighed
1-­‐2
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
beaker   represents   your   1st   aliquot.     Reweigh   the   beaker   containing   10   mL   of   water   and
record  the  mass.
Measure   another   10   mL   of   water   into   the   graduated   cylinder   and   pour   the   water   into   the
beaker;  this  water  is  your  2nd  aliquot.    Reweigh  and  record  the  mass  of  the  beaker  containing
20  mL  of  water.
Repeat  with  a  third  transfer  of  10  mL  of  water  to  the  beaker  (3rd  aliquot)  and  record  the  mass
of   the   beaker   containing   30   mL   of   water.     Use   a   thermometer   to   measure   the   temperature   of
the  water  to  the  nearest  degree.
Measure   and   record   the   mass   of   a   clean,   dry   150   mL   beaker.     As   accurately   as   possible,
measure   10   mL   of   water   using   a   10   mL   volumetric   pipet.     [Note:     It   is   not   necessary   to
measure  the  mass  of  the  empty  pipet.]  Your  instructor  will  demonstrate  the  proper  use  of  a
volumetric  pipet  and  pipet  bulb.    When  the  bottom  of  the  meniscus  of  water  lies  on  the  fill
line,  carefully  drain  the  pipet.    The  method  by  which  a  pipet  is  properly  drained  can  depend
on   the   type   of   pipet   bulb   used.     One   method   that   works   regardless   of   the   kind   of   bulb   used   is
to  remove  the  bulb,  place  the  tip  of  the  pipet  against  the  glass  of  the  beaker,  and  allow  the
liquid   to   drain   naturally   by   gravity.     When   properly   drained,   a   volumetric   pipet   will   retain
some   liquid   in   the   tip.     Blowing   this   liquid   out   will   deliver   more   water   than   expected   and
should   never   be   done.     Deliver   the   water   from   the   pipet   to   the   beaker   (this   is   your   1st
aliquot),  and  reweigh  the  beaker  containing  the  10  mL  of  water.
Measure  another  10  mL  of  water  into  the  volumetric  pipet  and  transfer  this  water  into  the
beaker  (this  is  the  2nd  aliquot).    Reweigh  and  record  the  mass  of  the  beaker  containing  20  mL
of  water.
Repeat   with   a   third   transfer   of   10   mL   of   water   from   the   pipet   to   the   beaker   (3rd   aliquot)   and
record  the  mass  of  the  beaker  containing  30  mL  of  water.    Use  a  thermometer  to  measure  the
temperature  of  the  water  to  the  nearest  degree.
When  finished  collecting  data,  dry  all  glassware  and  return  all  glassware  and  thermometers
to  their  original  locations.    Proceed  to  the  data  analysis  portion  of  the  experiment.

DATA  ANALYSIS

Part  1:    Which  piece  of  glassware  most  accurately  contains  a  stated  volume?
Show  your  work  for  all  calculations  in  the  space  provided  on  the  data  sheet.    Use  the  back
of  the  page  if  you  need  more  room.
Calculate   the   mass   of   water   by   subtracting   the   mass   of   the   empty   glassware   from   the   mass
of   the   glassware   containing   water.     Locate   the   density   of   water   at   the   measured
temperature  of  water  (refer  to  Table  1-­‐1  below).    Use  the  appropriate  density  of  water  to
calculate  the  volume  of  water  contained  in  each  piece  of  glassware.
The   absolute   error   of   a   measurement   is   defined   to   be   the   magnitude   of   the   difference
between  the  accepted  value  and  the  measured  value:
𝐴𝑏𝑠𝑜𝑙𝑢𝑡𝑒  𝑒𝑟𝑟𝑜𝑟   =     |  𝐴𝑐𝑐𝑒𝑝𝑡𝑒𝑑  𝑣𝑎𝑙𝑢𝑒   −    𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑑  𝑣𝑎𝑙𝑢𝑒  |
1-­‐3
(1)
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
The   percent   error   in   a   measurement   is   the   magnitude   of   the   absolute   error   divided   by   the
accepted  value,  multiplied  by  100:
𝑃𝑒𝑟𝑐𝑒𝑛𝑡  𝑒𝑟𝑟𝑜𝑟   =
!”#\$%&'(  !””#”
!””#\$%#&  !”#\$%
×  100
(2)
The  vertical  bars  in  Equations  (1)  and  (2)  represent  absolute  value.
Calculate  the  absolute  error  and  the  percent  error  for  each  piece  of  glassware.
Table  1-­‐1:    Density  of  Water  at  Various  Temperatures

Temperature  (°C)
Density  (g/mL)
16
0.9989
17
0.9988
18
0.9986
19
0.9984
20
0.9982
21
0.9980
22
0.9978
23
0.9975
24
0.9973
25
0.9970
26
0.9968
27
0.9965
28
0.9962

Rank   the   glassware   according   to   accuracy.     The   most   accurate   measurement   has   the
smallest  percent  error,  while  the  least  accurate  measurement  has  the  largest  percent  error.
Part  2:    Which  piece  of  glassware  most  accurately  delivers  a  stated  volume?
As  in  Part  1,  show  work  for  all  calculations  in  the  space  provided  on  the  data  sheet,  or  on
the  back  of  the  page.
Calculate  the  mass  of  the  first  aliquot  of  water  by  subtracting  the  mass  of  the  empty  beaker
(into   which   the   water   was   transferred)  from   the   mass   of   the   beaker   containing   10   mL   of
water.    Determine  the  mass  of  water  in  the  second  aliquot  by  subtracting  the  mass  of  the
beaker  containing  10  mL  of  water  from  the  mass  of  the  beaker  containing  20  mL  of  water.
Determine   the   mass   of   water   in   the   third   aliquot   by   subtracting   the   mass   of   the   beaker
containing  20  mL  of  water  from  the  beaker  containing  30  mL  of  water.    As  before,  use  the
density  of  water  at  the  temperature  you  measured  to  calculate  the  volume  of  water  in  each
aliquot.
Once  the  volume  of  each  aliquot  has  been  determined,  calculate  the  average  volume  of  an
aliquot   delivered   by   that   type   of   glassware.     Compare   the   average   aliquot   volumes   for   each
measuring  device  to  determine  which  one  more  accurately  delivers  10  mL  of  water.

1-­‐4
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
SAMPLE  CALCULATIONS
A   student   weighs   an   empty   150   mL   beaker   and   finds   the   mass   to   be   74.56   g.   She   then   adds
100  mL  of  water  and  finds  its  mass  to  be  176.23  g.  The  temperature  of  the  water  is  23°C.
What  is  the  calculated  volume  of  water?
(1)   Find  the  density  of  water  from  Table  1.
At  23°C,  the  density  of  water  is  0.9975  g/mL
(2)   Calculate  the  mass  of  water.
Mass  of  water  =  Mass  of  water  plus  beaker  –  Mass  of  empty  beaker
Mass  of  water  =  176.23  g  –  74.56  g  =  101.67  g
(3)   Calculate  the  volume  of  water.
!
Use  the  equation  𝑉 =    (volume  =  mass  divided  by  density)
!
𝑉=
101.67  𝑔
= 101.9  𝑚𝐿
𝑔
0.9975   𝑚𝐿

WHY  IS  THIS  LAB  GREEN?
Only  water  was  used  in  this  experiment.

REFERENCE

Lide,   D.   R.   (Ed.)   (1990).   CRC   Handbook   of   Chemistry   and   Physics   (70th   Ed.).   Boca   Raton
(FL)  :  CRC  Press

1-­‐5
CHEM  1111
Experiment  1
Name:

Section:
Score:
Experiment  1  Prelab  Assignment

A  student  collects  the  following  data  when  measuring  the  volume  of  a  100  mL  graduated
cylinder:
Mass  of  empty  graduated  cylinder  =  45.446  g
Mass  of  graduated  cylinder  +  100  mL  water  =  145.397  g
Temperature  of  water  =  21.8°C

1.   What   is   the   density   of   the   water?     (Round   the   temperature   to   the   nearest   degree   and
look  up  the  density  in  Table  1.

2.   (a)   What   is   the   mass   of   the   water?     Report   your   answer   to   the   correct   number   of
significant  figures.

(b)   Justify  the  number  of  significant  figures  in  your  answer  to  Part  (a).

3.   (a)   What   is   the   volume   of   the   water?     Report   your   answer   to   the   correct   number   of
significant  figures.

(b)   Justify  the  number  of  significant  figures  in  your  answer  to  Part  (a).

4.   Calculate  the  percent  error  in  this  measurement.

1-­‐6

CHEM  1111
Experiment  1
Name:

Section:
Score:
Experiment  1  Report  Sheet

Part  1:    Which  piece  of  glassware  most  accurately  contains  a  stated  volume?

Measured  Data
Glassware:
150  mL  Beaker
100  mL
Cylinder
100  mL

A
Mass  of  empty  glassware  (grams)
B
Mass  of  glassware  containing  100
mL  water  (grams)

C
Temperature  of  water  (°C)

D
Density  of  water

Calculated  Results
E
Mass  of  water  (grams)
F
Volume  of  water  (mL)
G
Accepted  volume  (mL)
H
Absolute  error
I
Percent  error

100.
100.0
100.0

Show  work  for  all  calculations  in  the  space  below  and/or  on  the  back  of  this  page:

Rank  the  glassware  from  MOST  accurate  to  LEAST  accurate:

1-­‐7

CHEM  1111
Experiment  1
Name:

Section:

Part  2:    Which  piece  of  glassware  most  accurately  delivers  a  stated  volume?

Measured  Data
Glassware  used  to  Measure
10  mL  Graduated  Cylinder
10  mL  Aliquots:
10  mL  Volumetric  Pipet

J
Mass  of  empty  beaker  (grams)
K
Mass  of  beaker  containing  Aliquot
1  (grams)

L
Mass  of  beaker  containing  Aliquot
1  and  Aliquot  2  (grams)

M
Mass  of  beaker  containing  Aliquots
1,  2,  and  3  (grams)

N
Temperature  of  water  (°C)
O
Density  of  water

Calculated  Results
P
Mass  of  Aliquot  1  (grams)

Q
Mass  of  Aliquot  2  (grams)

R
Mass  of  Aliquot  3  (grams)
S
Volume  of  Aliquot  1  (mL)
T
Volume  of  Aliquot  2  (mL)
U
Volume  of  Aliquot  3  (mL)
V
Average  volume  of  each  aliquot
(mL)

Show  work  for  all  calculations  in  the  space  below  and/or  on  the  back  of  this  page:

Which  piece  of  glassware  more  accurately  delivered  10  mL  of  water?
1-­‐8
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
Experiment  2
The  Density  of  Liquids  and  Solids

LEARNING  OBJECTIVES

Reinforce  skills  from  Experiment  1  (measurement  of  mass  and  temperature)
Understand  relationships  between  mass,  volume  and  density

INTRODUCTION
Part  1:  Density  of  a  liquid
The  density  (d)  of  a  substance  is  the  ratio  of  its  mass  (m)  to  its  volume  (V):
!
𝑑 =
!
(1)
Based   on   this   definition,   it   is   clear   that   both   the   mass   and   the   volume   must   be   known
precisely  to  obtain  a  good  measure  of  the  density  of  a  substance.
A  pycnometer  is  an  instrument  that  is  used  to  determine  the  density  of  a  liquid  with  a  high
degree  of  accuracy.    It  is  usually  made  out  of  glass  and  is  equipped  with  a  stopper  that  has  a
small  hole  through  the  center.    This  small  hole  allows  air  bubbles  to  escape  and   produces  a
repeatable   measure   of   volume.     To   determine   the   density   of   a   liquid   accurately,   both   the
mass   and   volume   must   be   known   accurately.     In   this   experiment,   a   stoppered   50   mL
Erlenmeyer   flask   will   be   used   as   a   simple   pycnometer.   By   difference,   it   is   possible   to
determine  precisely  the  mass  of  the  liquid  contained  within  the  stoppered  flask  when  it  is
filled.     Determination   of   the   volume   occupied   by   the   liquid   is   somewhat   less
straightforward.     The   full   volume   of   the   flask   IS   NOT   50   mL;   the   markings   on   an
Erlenmeyer  flask  do  not  provide  a  very  accurate  measure  of  volume.

Determining  the  volume  of  the  flask:
Because   the   density   of   water   at   a   particular   temperature   is   known   to   a   high   degree   of
accuracy,  we  will  use  water  to  determine  the  volume  of  the  flask.    Initially,  the  mass  of  the
empty  dry  stoppered  flask  will  be  measured.  The  flask  will  then  be  filled  completely  with
water,   and   the   mass   of   the   filled   stoppered   flask   will   be   measured.     The   mass   of   water
contained  in  the  flask  may  then  easily  be  calculated  by  difference:
𝑀𝑎𝑠𝑠  𝐻! 𝑂 = 𝑀𝑎𝑠𝑠  𝑜𝑓  𝑓𝑖𝑙𝑙𝑒𝑑  𝑠𝑡𝑜𝑝𝑝𝑒𝑟𝑒𝑑  𝑓𝑙𝑎𝑠𝑘 − 𝑀𝑎𝑠𝑠  𝑜𝑓  𝑒𝑚𝑝𝑡𝑦  𝑠𝑡𝑜𝑝𝑝𝑒𝑟𝑒𝑑  𝑓𝑙𝑎𝑠𝑘
(2)
The  temperature  of  the  water  will  be  measured  (to  the  nearest  degree),  and  Table  2-­‐1  will
be   used   to   find   the   density   of   water   at   the   measured   temperature.     The   volume   of   water
contained   within   the   filled   stoppered   flask   can   be   determined   by   rearranging   Equation   (1),
using  the  mass  of  the  water  and  the  density  at  the  measured  temperature.    We  will  assume
that   the   volume   of   water   contained   within   the   filled   stoppered   flask   is   equal   to   the
overall  volume  of  the  flask.    This  volume  will  be  constant  throughout  the  remainder  of  the
experiment.
2-­‐1
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
Table  2-­‐1:    Density  of  Water  at  Various  Temperatures

Temperature  (°C)
Density  (g/mL)
16
0.9989
17
0.9988
18
0.9986
19
0.9984
20
0.9982
21
0.9980
22
0.9978
23
0.9975
24
0.9973
25
0.9970
26
0.9968
27
0.9965
28
0.9962

Determining  the  density  of  a  liquid:
To   calculate   the   density   of   an   unknown   liquid,   we   will   fill   the   flask   completely   with   the
liquid  and  determine  the  mass.
𝑀𝑎𝑠𝑠  𝑙𝑖𝑞𝑢𝑖𝑑 = 𝑀𝑎𝑠𝑠  𝑜𝑓  𝑓𝑖𝑙𝑙𝑒𝑑  𝑠𝑡𝑜𝑝𝑝𝑒𝑟𝑒𝑑  𝑓𝑙𝑎𝑠𝑘 − 𝑀𝑎𝑠𝑠  𝑜𝑓  𝑒𝑚𝑝𝑡𝑦  𝑠𝑡𝑜𝑝𝑝𝑒𝑟𝑒𝑑  𝑓𝑙𝑎𝑠𝑘     (3)
The  volume  of  the  liquid  is  equal  to  the  overall  volume  of  the  flask.    The  density  of  the
liquid  can  then  be  calculated  from  Equation  (1).

Part  2:    Density  of  a  solid
Because   a   liquid   can   completely   fill   a   container   of   any   shape,   it   is   easy   to   determine
accurately  a  liquid’s  volume.    In  this  experiment,  the  volume  of  the  liquid  is  simply  equal  to
the  overall  volume  of  the  flask.    Determining  the  volume  of  a  solid  is  slightly  more  difficult
because   the   flask   cannot   be   completely   filled   with   the   solid   (air   would   be   trapped   in   the
flask   between   the   solid   pieces).     To   determine   the   volume   of   an   irregularly   shaped   solid,
the   concept   of   displacement   will   be   used.   Any   solid   object,   when   placed   in   water,   will
displace   a   volume   of   water   that   is   equal   to   the   volume   of   the   solid.     We   will   place   a   solid   in
the   flask,   and   then   fill   the   remainder   of   the   flask   completely   with   water.     The   overall
volume  of  the  flask  (known)  will  be  equal  to  the  sum  of  the  volume  occupied  by  the  solid
and  the  volume  of  the  added  water.
Determining  the  mass  of  the  solid:
After   partially   filling   the   flask   with   a   solid   and   recording   the   mass   of   the   flask   containing
the  solid,  the  mass  of  the  solid  may  be  easily  calculated:
𝑀𝑎𝑠𝑠  𝑠𝑜𝑙𝑖𝑑 = 𝑀𝑎𝑠𝑠  𝑜𝑓𝑠𝑡𝑜𝑝𝑝𝑒𝑟𝑒𝑑  𝑓𝑙𝑎𝑠𝑘  𝑝𝑙𝑢𝑠  𝑠𝑜𝑙𝑖𝑑 − 𝑀𝑎𝑠𝑠  𝑜𝑓  𝑒𝑚𝑝𝑡𝑦  𝑠𝑡𝑜𝑝𝑝𝑒𝑟𝑒𝑑  𝑓𝑙𝑎𝑠𝑘  (4)
2-­‐2
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
Determining  the  volume  of  the  solid:
To  the  flask  partially  filled  with  a  solid,  water  will  be  added  until  the  flask  is  filled  and  no
air   bubbles   are   present.       Now,   the   volume   of   the   flask   is   occupied   with   both   solid   and
water.    In  other  words,
𝑉𝑜𝑙𝑢𝑚𝑒  𝑜𝑓  𝑓𝑙𝑎𝑠𝑘 = 𝑉𝑜𝑙𝑢𝑚𝑒  𝑜𝑓  𝑠𝑜𝑙𝑖𝑑 + 𝑉𝑜𝑙𝑢𝑚𝑒  𝑜𝑓  𝐻! 𝑂                                        (5)
The   volume   of   the   water   in   the   flask   can   be   determined   from   the   mass   of   water   and   its
density,  using  Equation  (1).    The  mass  of  the  water  is  calculated  by  difference:
𝑀𝑎𝑠𝑠  𝐻! 𝑂 = 𝑀𝑎𝑠𝑠  𝑜𝑓𝑠𝑡𝑜𝑝𝑝𝑒𝑟𝑒𝑑  𝑓𝑙𝑎𝑠𝑘 +  𝑠𝑜𝑙𝑖𝑑 +   𝐻! 𝑂 − 𝑀𝑎𝑠𝑠  𝑜𝑓  𝑠𝑡𝑜𝑝𝑝𝑒𝑟𝑒𝑑  𝑓𝑙𝑎𝑠𝑘  𝑝𝑙𝑢𝑠  𝑠𝑜𝑙𝑖𝑑
(6)
Once  the  volume  of  water  is  determined,  the  volume  of  the  solid  can  be  easily  calculated  by
rearranging  Equation  (5):
𝑉𝑜𝑙𝑢𝑚𝑒  𝑜𝑓  𝑠𝑜𝑙𝑖𝑑   = 𝑉𝑜𝑙𝑢𝑚𝑒  𝑜𝑓  𝑓𝑙𝑎𝑠𝑘 − 𝑉𝑜𝑙𝑢𝑚𝑒  𝑜𝑓  𝐻! 𝑂                                  (7)
The  density  of  the  solid  is  calculated  by  substituting  the  mass  of  the  solid  and  the  volume  of
the  solid  into  Equation  (1).

Part  3:  Compare  two  methods  of  density  determination
In  this  portion  of  the  experiment,  a  50  mL  graduated  cylinder  will  be  used  to  measure  the
density  of  both  a  liquid  and  a  solid.
Determining  the  density  of  a  liquid  (Method  2)
The  volume  of  a  liquid  can  be  measured  directly  using  a  graduated  cylinder.    The  mass  of
the  liquid  is  calculated  by  subtracting  the  mass  of  the  empty  graduated  cylinder  from  the
mass  of  the  cylinder  containing  the  unknown  liquid.
𝑀𝑎𝑠𝑠  𝑙𝑖𝑞𝑢𝑖𝑑 = 𝑀𝑎𝑠𝑠  𝑜𝑓  𝑔𝑟𝑎𝑑  𝑐𝑦𝑙𝑖𝑛𝑑𝑒𝑟  𝑤𝑖𝑡ℎ  𝑙𝑖𝑞𝑢𝑖𝑑  – 𝑀𝑎𝑠𝑠  𝑜𝑓  𝑒𝑚𝑝𝑡𝑦  𝑔𝑟𝑎𝑑  𝑐𝑦𝑙𝑖𝑛𝑑𝑒𝑟   (8)
Once   the   mass   of   the   liquid   has   been   calculated,   the   density   can   be   determined   from
Equation  (1).
Determining  the  density  of  a  solid  (Method  2)
The  mass  of  a  solid  can  be  measured  directly  using  an  analytical  balance.    If  the  solid  is  then
added  to  a  known  volume  of  water  in  a  graduated  cylinder,  the  new  volume  reading  after
displacement  allows  for  the  calculate  of  the  volume  of  the  solid  alone:
𝑉𝑜𝑙𝑢𝑚𝑒  𝑜𝑓  𝑠𝑜𝑙𝑖𝑑 = 𝑉𝑜𝑙𝑢𝑚𝑒  𝑜𝑓  𝑠𝑜𝑙𝑖𝑑  𝑎𝑛𝑑  𝑤𝑎𝑡𝑒𝑟  – 𝑉𝑜𝑙𝑢𝑚𝑒  𝑜𝑓  𝑤𝑎𝑡𝑒𝑟
Equation  (1)  can  be  used  to  calculate  the  density  of  the  solid  after  the  volume  has  been
determined.
2-­‐3
(9)
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
PROCEDURE
Part  1:  Density  of  a  liquid
Determine   the   mass   of   a   clean   dry   50   mL   Erlenmeyer   flask   and   stopper.     Fill   the   flask
completely  with  water.    Use  a  thermometer  to  measure  the  temperature  of  the  water  to  the
nearest  degree.    Place  a  stopper  in  the  flask  such  that  no  air  is  trapped.    If  you  see  any  air
bubbles,  remove  the  stopper  and  add  more  water.    Make  sure  that  the  outside  of  the  flask  is
dry,  and  record  the  mass  of  the  filled,  stoppered  flask.    Empty  and  dry  the  flask  and  stopper.
Your   instructor   should   provide   instructions   as   to   how   to   rapidly   dry   the   flask.     It   is
important  to  use  the  same  flask  and  stopper  throughout  the  experiment.    Refill  the  flask
with  an  unknown  liquid  (be  sure  to  record  the  unknown  number)  and  stopper  the  flask  as
before   so   that   no   air   is   trapped.     Dry   off   the   outside   of   the   flask,   and   record   the   mass   of   the
stoppered   flask   containing   the   unknown   liquid.     Pour   the   unknown   liquid   back   into   its
original  bottle.    Rinse  the  50  mL  Erlenmeyer  flask  with  water  before  drying  the  flask  and
stopper  according  to  your  instructor’s  directions.
Part  2:    Density  of  a  solid
Half-­‐fill   the   clean,   dry   50   mL   Erlenmeyer   flask   with   an   unknown   solid   (be   sure   to   record
the  unknown  number).    Place  the  stopper  in  the  flask  and  record  the  mass  of  the  stoppered
flask   containing   the   solid.     Slowly  add  water  to  the  flask  containing  the  solid.     As   the   water
is  added  be  sure  to  swirl  the  flask  around  to  eliminate  any  air  bubbles  trapped  between  the
solid  pieces.    Continue  adding  water  until  the  flask  is  completely  filled  and  there  is  no  air
trapped  when  the  flask  is  stoppered.    Measure  and  record  the  mass  of  the  stoppered  flask
containing  water  and  solid.    Carefully  pour  the  water  out  of  the  flask,  and  return  the  solid  to
be  dried  as  directed  by  your  instructor.    Do  not  mix  wet  solids  with  dry  solids!
Part  3:  Compare  two  methods  of  density  determination
Determining  the  density  of  a  liquid  (Method  2)
Weigh   and   record   the   mass   of   a   clean   dry   50   mL   graduated   cylinder.     Fill   the   graduated
cylinder   as   accurately   as   possible   with   50   mL   of   the   same   unknown   liquid   that   you   used
earlier.    Weigh  and  record  the  mass  of  the  graduated  cylinder  plus  the  liquid.    Be  sure  to
use   the   same   unknown   liquid   used   in   the   first   part   of   this   experiment.     Return   the
unknown  liquid  to  the  original  bottle  for  reuse.

Determining  the  density  of  a  solid  (Method  2)
Place  about  25  mL  of  water  in  a  clean  dry  50  mL  graduated  cylinder.    Record  the  volume  of
the  water  to  one  decimal  place.    Place  a  weigh  boat  on  a  balance  and  re-­‐zero  (or  tare)  the
balance.     Add   a   small   amount   (try   for   around   10   -­‐   20   mL)   of   solid   to   the   weigh   boat   and
record  the  mass.    Carefully  place  the  solid  in  the  graduated  cylinder  containing  water  and
record   the   volume   to   which   the   water   rises.     Carefully   pour   the   water   out   of   the   graduated
cylinder  and  return  the  solid  to  your  instructor  as  directed.    Clean  and  dry  any  glassware
and  return  all  glassware  and  thermometers  to  their  original  locations.

2-­‐4
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
SAMPLE  CALCULATIONS
A   student   weighs   an   empty   stoppered   Erlenmeyer   flask   and   determines   the   mass   to   be
41.626  g.    When  the  flask  is  filled  completely  with  water  at  a  temperature  of  25°C,  the  mass
of  the  filled  stoppered  flask  is  96.720  g.    What  is  the  overall  volume  of  the  flask?
(1)   Find  the  density  of  water  from  Table  1.
At  25°C,  the  density  of  water  is  0.9970  g/mL.
(2)   Calculate  the  mass  of  water.
Mass  of  water  =  Mass  of  filled  stoppered  flask  –  Mass  of  empty  stoppered  flask
Mass  of  water  =  96.720  g  –  41.626  g  =  55.094  g
(3)   Calculate  the  volume  of  water  which  equals  the  overall  volume  of  the  flask.
𝑉 = 55.094  𝑔  ×
1  𝑚𝐿
= 55.26  𝑚𝐿
0.9970  𝑔
The  same  flask  is  then  filled  completely  with  a  different  unknown  liquid.    The  mass  of  the
filled  stoppered  flask  is  85.381  g.    What  is  the  density  of  the  unknown  liquid?
(4)   Calculate  the  mass  of  the  liquid.
Mass  of  liquid  =  Mass  of  filled  stoppered  flask  –  Mass  of  empty  stoppered  flask
Mass  of  liquid  =  85.318  g  –  41.626  g  =  43.755  g
(5)   Calculate  the  density  of  the  liquid.
𝑚
43.755  𝑔
𝑔
=
= 0.7918   𝑚𝐿
𝑉
55.26  𝑚𝐿
The   same   flask   is   partially   filled   with   an   irregularly   shaped   solid.     The   mass   of   the
stoppered   flask   plus   the   solid   is   200.16   g.     Enough   water   is   added   to   fill   the   flask
completely.     The   mass   of   the   stoppered   flask   containing   the   solid   and   water   is   235.14   g.
What  is  the  density  of  the  solid?
𝑑 =
(6)   Calculate  the  mass  of  the  solid.
Mass  of  solid  =  Mass  of  stoppered  flask  plus  solid  –  Mass  of  empty  stoppered  flask
Mass  of  solid  =  200.16  g  –  41.626  g  =  158.53  g
(7)   Calculate  the  mass  of  the  added  water.
Mass  of  H2O  =  Mass  of  stoppered  flask  +  solid  +  H2O  –  Mass  of  stoppered  flask  +  solid
Mass  of  H2O  =  235.14  g  –  200.16  g  =  34.98  g
(8)   Calculate  the  volume  of  the  added  water.
𝑉 = 34.98  𝑔  ×
1  𝑚𝐿
= 35.09  𝑚𝐿
0.9970  𝑔

2-­‐5
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
(9)   Calculate  the  volume  of  the  solid.
Volume  of  solid  =  Volume  of  flask  –  Volume  of  water
Volume  of  solid  =  55.26  mL  –  35.09  mL  =  20.17  mL
(10)  Calculate  the  density  of  the  solid.
𝑑 =
𝑚
158.53  𝑔
𝑔
=
= 7.860   𝑚𝐿
𝑉
20.17  𝑚𝐿

WHY  IS  THIS  LAB  GREEN?
All   the   liquids   used   in   this   experiment   are   recycled   through   reuse   in   our   labs.     The   solids   are
reusable  and  only  need  to  be  dried  between  lab  classes.

REFERENCE
Lide,   D.   R.   (Ed.)   (1990).   CRC   Handbook   of   Chemistry   and   Physics   (70th   Ed.).   Boca   Raton   (FL)
:  CRC  Press

2-­‐6
CHEM  1111
Experiment  2
Name:

Section:
Score:
Experiment  2  Prelab  Assignment

1.   A   student   finds   that   the   mass   of   a   stoppered   50   mL   Erlenmeyer   flask   is   46.976   g.     After
filling  the  flask  with  water  and  replacing  the  stopper,  the  mass  is  found  to  be  101.813  g.
The  temperature  of  the  water  is  23°C.    Calculate  the  volume  of  water  contained  in  the

2.   The  same  flask  used  in  Question  1  is  emptied,  dried,  and  then  filled  with  an  unknown
liquid.    The  mass  of  the  stoppered  flask  containing  the  liquid  is  found  to  be  105.184  g.
Determine  the  density  of  the  unknown  liquid.

3.   Consider   the   situation   described   in   Question   2,   but   suppose   that   an   air   bubble   is
present   in   the   flask   that   was   not   noticed   before   the   stoppered   flask   containing   the
liquid   was   weighed.     Compared   to   the   “true”   value,   will   the   calculated   density   be   too
low  or  too  high  as  a  result  of  this  error?    Explain  your  reasoning.

4.   In  this  experiment,  when  the  density  of  the  solid  is  determined,  the  volume  of  the  solid
is   found   by   subtracting   the   volume   of   water   (in   a   flask   filled   with   solid   and   water)   from
the   overall   volume   of   the   flask.     What   principle   is   being   used   here   to   determine   the
volume  of  the  solid?

2-­‐7

CHEM  1111
Experiment  2
Name:

Section:
Score:
Experiment  2  Report  Sheet

Calculated  Data  and  Results:    SHOW  YOUR  WORK  for  all
calculations!!!    Be  sure  to  include  UNITS  for  all  results.
Volume  of  the  flask:
Collected  Data:    Be  sure  to  include  UNITS  for  all  measurements.
A
Mass  of  empty  flask  and  stopper

B
Mass  of  stoppered  flask  filled  with
water

C
Temperature  of  water

D
Density  of  water  (refer  to  Table  1)

E
Mass  of  stoppered  flask  filled  with
unknown  liquid

F
Mass  of  stoppered  flask  half-­‐filled
with  unknown  solid

G
Mass  of  stoppered  flask  +  solid  +
water

Unknown  Solid  (Part  2)
Mass  of  water

I
Volume  of  water  =  volume  of  the  flask

Density  of  unknown  liquid:
J
Mass  of  unknown  liquid

K
Density  of  unknown  liquid

Density  of  unknown  solid:

Record  your  unknown  codes  below!
Unknown  Liquid  (Part  1)
H
L
Mass  of  unknown  solid

M
Mass  of  water  added  to  unknown  solid

N
Volume  of  water  added  to  unknown
solid

O
Volume  of  unknown  solid

P
Density  of  unknown  solid

2-­‐8

CHEM  1111
Experiment  2
Name:

Section:

Record  your  unknown  codes  below!
Collected  Data:    Be  sure  to  include  UNITS  for  all  measurements.
Q
Mass  of  empty  graduated  cylinder

R
Mass  of  graduated  cylinder
containing  unknown  liquid

S
Mass  of  solid  used

T
Volume  of  water  in  graduated
cylinder

Volume  of  water  and  solid  in

U

Unknown  Liquid

Unknown  Solid

Your   instructor   will   provide   you   with   the   densities   of   the
unknown   liquids   and   solids.     Calculate   your   percent   error
for  the  density  of  the  liquid  and  the  solid  from  each  of  the
two  methods.
50  mL
Erlenmeyer
50  mL
cylinder

Calculated  Data  and  Results:    SHOW  YOUR  WORK  for  all
calculations!!!    Be  sure  to  include  UNITS  for  all  results.

Liquid  (percent  error)
V
Mass  of  the  liquid

W
Density  of  the  liquid

X
Volume  of  the  solid

Y
Density  of  the  solid

Which   method   did   you   find   produced   more   accurate
results?

Do   you   feel   that   the   50   mL   Erlenmeyer   flask   was   effective
at  approximating  the  use  of  a  pycnometer?
Solid  (percent  error)

2-­‐9

Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
Experiment  3
How  Much  Sugar  is  in  a  Can  of  Soda?

LEARNING  OBJECTIVES

Determine  the  mass  of  sugar  in  a  can  of  soda
Prepare  solutions  quantitatively  using  a  volumetric  flask
Prepare  and  use  a  calibration  curve
INTRODUCTION
If  you  were  to  measure  out  identical  volumes  of  regular  soda  and  diet  soda,  you  would  find
that   the   two   liquids   have   different   masses.     This   difference   in   the   mass   of   the   two   liquids   is
best  understood  by  looking  at  the  mass  per  unit  volume  (or  density)  of  the  two  liquids:
!
𝑑 =
!
(1)
Density  is  a  convenient  quantity  to  use  for  comparative  purposes  because  it  is  independent
of   the   volume   of   liquid   used.     In   other   words,   density   is   an   intensive   property.     An
intensive  property  is  one  that  is  independent  of  the  amount  of  substance.    For  this  reason,
the  densities  of  two  different  solutions  can  be  compared  without  needing  to  have   identical
solution  volumes.
When   comparing   regular   soda   and   diet   soda,   it   is   found   that   regular   soda   is   more   dense
than   its   sugar-­‐free   relative.     To   understand   why,   a   molecular   view   of   the   two   substances
must   be   examined.     Obviously,   the   main   difference   between   the   two   is   the   presence   of
dissolved  sugar  in  regular  soda,  which  is  absent  in  diet  soda.    Since  diet  soda  lacks  sugar,  its
density  is  somewhat  lower  than  that  of  regular  soda.    To  a  first  approximation,  soda  can  be
represented  as  a  solution  of  sugar  dissolved  in  water.    As  the  amount  of  sugar  dissolved  in  a
given   volume   of   water   increases,   so   does   the   density   of   the   resulting   solution.     This
provides  an  ideal  means  by  which  the  mass  of  sugar  in  a  soda  can  be  determined.
In   this   experiment,   the   relationship   between   the   mass   of   dissolved   sugar   and   density   of
several  sugar  water  solutions  will  be  determined  through  the  use  of  a  calibration  curve.    A
calibration   curve   is   constructed   using   known   quantities.     In   this   case,   you   will   prepare
solutions  of  known  volume  using  a  known  mass  of  dissolved  sugar.    After  determining  the
density   of   each   solution,   you   will   prepare   a   graph   of   density   vs   mass   of   dissolved   sugar.
You  will  then  graphically  determine  the  relationship  between  the  two  quantities.    After  you
determine  the  density  of  a  sample  of  soda,  you  will  use  your  calibration  curve  to  estimate
the  mass  of  sugar  present  in  your  sample,  and  also  in  a  12  fluid  ounce  serving  of  the  soda.

Scientific  Graphs:
This  experiment  will  also  serve  to  introduce  you  to  scientific  graphing.    Whenever  you  are
asked  to  produce  a  graph  from  laboratory  data,  all  of  the  following  criteria  must  be  met:
1. All  graphs  must  have  a  descriptive  title
3-­‐1
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
2. Axes  must  be  labeled  with  an  appropriate  name  and  units
3. The  data  should  occupy  the  full  space  of  the  graph
4. The  minimum  size  of  a  graph  should  be  half  the  size  of  a  standard  sheet  of  paper
5. When  plotting  a  best  fit  line  to  the  data,  the  line  and  equation  (if  applicable)  should
be  shown  explicitly  on  the  graph
6. The  independent  variable  is  plotted  along  the  x-­‐axis,  and  the  dependent  variable  is
plotted  on  the  y-­‐axis

Figure   3–1   shows   an   example   of   an   acceptable   scientific   graph   of   raw   data.     Figure   3–2
demonstrates  the  proper  way  to  represent  a  linear  fit  on  a  graph.

Figure  3-­‐1:    Scientific  graph  of  raw  data

3-­‐2
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab

Figure  3-­‐2:    Graph  including  best-­‐fit  straight  line

Graphing  Using  Microsoft  Excel:
The   basic   steps   required   to   graph   data   and   perform   linear   regressions   with   Excel   are
outlined  below.    These  instructions  apply  to  Excel  2013.
Basic  Graphing:
1. With  the  program  open,  enter  the  data  to  be  graphed  in  the  cells.    Enter  the  data  to
be   plotted   along   the   x-­‐axis   in   one   column,   followed   by   the   associated   data   to   be
plotted  along  the  y-­‐axis  in  the  adjacent  column.
2. Click  and  drag  the  mouse  to  highlight  all  the  data  to  be  graphed.
3. Click  on  the  “Insert”  tab  at  the  top  of  the  screen
4. Select  the  “Scatter”  icon,  followed  by   the  unconnected  points  icon  for  the  chart  sub-­‐
type.    At  this  point  a  graph  will  appear  on  your  screen.
5. Select   the   “Format”   tab   under   “Chart   Tools”.     Use   the   drop-­‐down   menu   at   the   upper
left   of   the   ribbon   to   choose   “Chart   Title”   or   the   appropriate   axis.     To   label   an   axis,
click   on   the   “+”   icon   to   the   right   of   the   graph   and   be   sure   that   “Axis   Titles”   box   is
checked.

3-­‐3
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
Adding  a  Linear  Trendline  to  a  Graph:
1. Click  on  the  “+”  icon  to  the  right  of  the  graph,  and  check  the  “Trendline”  box.    Click
on   the   arrow   to   the   right   to   select   the   “Linear”   option.       A   best   fit   line   will   now
appear  on  your  graph.
2. To   display   the   equation   of   the   line   (and   to   access   other   options   related   to   the
trendline)  right  click  on  the  Trendline  on  the  graph  and  select  “Format  Trendline”.
Click  on  the  “Display  Equation  on  Chart”  box  and  then  hit  close.

Graphing  By  Hand:
Using  your  collected  data,  construct  a  graph  of  density  (y)  vs.  mass  of  dissolved  sugar  (x).
Use  the  graph  paper  provided  with  the  report  sheet  (last  page  of  this  handout).    Remember,
you  want  your  data  to  fill  as  much  of  the  graph  paper  as  possible!    If  your  instructor  does
not  specify  the  smallest  division  to  use  on  each  axis,  you  use  the  following  strategy:
1. Determine   the   range   of   values   along   the   axis   by   subtracting   the   smallest   value   from
the  largest  value.
Suppose   your   minimum   mass   of   sugar   used   was   0   g,   and   your   maximum   mass   of
sugar  used  was  15.770  g.    The  range  of  values  along  the  x-­‐axis  would  be:
15.770  𝑔 − 0  𝑔 = 15.770  𝑔
If   the   minimum   density   was   0.9951   g/mL   and   the   maximum   density   was   1.056
g/mL,  the  range  of  values  along  the  y-­‐axis  would  be:
1.056
𝑔
𝑚𝐿 − 0.9951
𝑔
𝑚𝐿 = 0.061
𝑔
𝑚𝐿
2. Count  the  number  of  divisions  along  each  axis.
In  the  graph  paper  provided  with  this  handout,  there  are  40  divisions  along  the  x-­‐
axis,  and  40  divisions  along  the  y-­‐axis.
3. Calculate   the   size   of   the   smallest   division   on   each   axis   by   taking   the   range   of   values,
and   dividing   by   the   number   of   divisions.     Round   this   quotient   UP   to   a   convenient
(i.e.  ends  in  0  or  5)  value!
!”.!!”  !
𝑔
The  smallest  division  along  the  x-­‐axis  =
= 0.39   𝑑𝑖𝑣
!”  !”#
Since  0.39  is  not  a  convenient  number,  round  UP  so  the  smallest  division  on  the  x-­‐
axis  is  0.40  g.
The  smallest  division  along  the  y-­‐axis  =
!.!”#
!
!”;
!”  !”#
!
= 0.001525   !” 𝑑𝑖𝑣
Round   UP   so   the   smallest   division   on   the   y-­‐axis   is   0.0020   g/mL.     [Note:     If   the
smallest  division  were  rounded  DOWN  to  0.0015  g/mL,  the  plotted  data  would  not
fit  on  the  graph  paper!    We  always  round  UP  when  calculating  the  smallest  division
to  insure  that  the  data  fits  on  the  graph  paper  being  used.
3-­‐4
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
After   your   data   is   plotted,   use   a   ruler   to   draw   the   best   fit   straight   line   through   your   data
points.    If  your  graph  includes  an  origin  (x  =  0,  y  =  0),  the  best-­‐fit  line  should  pass  through
the  origin.    Don’t  connect  the  dots!    Try  to  draw  a  line  that  passes  through  the  origin,  and
also   touches   or   comes   close   to   as   many   of   your   plotted   data   points   as   possible.     Remember
to   label   both   axes   with   units,   and   to   give   a   descriptive   title   to   your   graph!     In   this
experiment,   your   graph   represents   the   relationship   between   the   density   of   a   solution   of
sugar   water   (something   that   can   be   determined   experimentally)   and   the   mass   of   sugar
used  to  prepare  the  solution  (something  that  cannot  be  measured  directly  for  an  unknown,
like  a  sample  of  soda).

PROCEDURE
You  will  prepare  five  sugar  water  solutions.    Each  solution  should  have  a  different  mass  of
dissolved  sugar  covering  a  range  from  about  2  to  about  16  grams  of  sugar  per  100  mL  of
solution  volume.
To   make   the   solutions   in   an   accurate   manner,   they   must   be   prepared   in   a   100   mL
volumetric   flask,   which   is   designed   for   accurate   measurement   of   this   volume   of   solution.
Note  that  there  is  always  uncertainty  associated  with  volumetric  glassware.    For  significant
figure   considerations,   we   will   assume   that   the   volume   of   the   flask   (and   therefore   the
volume   of   each   solution)   is   accurate   to   ±   0.1   mL.     As   a   consequence,   the   volume   of   each
solution  will  be  considered  to  be  100.0  mL  (4  significant  figures).
As  shown  in  Figure  3–3,  a  volumetric  flask  is  marked  with  one  fill  line,  somewhere  on  the
neck.     When   filled   to   the   marked   line,   the   flask   accurately   holds   the   stated   volume.   To   fill   a
volumetric   flask,   it   is   best   to   bring   the   fluid   to   the   line   carefully   using   a   transfer   pipet   to
insure  that  the  volume  is  accurate.    The  volume  will  not  be  known  accurately  if  the  flask  is
overfilled  via  addition  of  liquid  above  the  fill  line.    Additionally,  if  water  is  present  on  the
sides   of   the   flask   above   the   fill   line,   the   result   will   be   a   solution   that   is   more   dilute   than
intended.

FILL  LINE

Figure  3–3:    A  volumetric  flask
Before  preparing  any  sugar  water  solutions,  you  should  measure  the  mass  of  a  clean,  dry,
empty   volumetric   flask   with   stopper.     If   you   use   the   same   flask   and   stopper   for   every
solution,  you  only  need  to  measure  this  mass  once  at  the  beginning  of  the  experiment.
3-­‐5
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
You  need  to  know  the  mass  of  sugar  used  to  prepare  each  solution.    Place  a  weigh  boat  on
the  balance  and  tare  (or  re-­‐zero)  the  balance  so  that  it  reads  zero  with  the  weigh  boat  on
the  balance.    Weigh  out  (and  record)  the  desired  mass  of  sugar.
Very  carefully  transfer  the  sugar  to  the  flask.    It  is  important  that  all  the  weighed  sugar  be
transferred  to  the  flask.    Using  a  funnel  to  transfer  the  sugar  to  the  flask  may  help  you  avoid
spills.    Your  instructor  will  demonstrate  the  best  approach  to  take  for  this  operation  if  an
appropriately  sized  funnel  is  not  available  in  your  lab.
Add  water  to  the  flask  until  the  bottom  portion  (the  round  part)  is  approximately  half  full.
Swirl  the  flask  to  dissolve  the  sugar.    Do  not  shake  the  flask.    Shaking  or  violent  swirling
will  cause  water  to  collect  above  the  fill  line  and  will  result  in  inaccurate  data.
Once   the   sugar   has   completely   dissolved,   add   water   carefully   until   the   level   is   slightly
below   the   fill   line.     To   avoid   adding   too   much   water,   add   the   last   portion   carefully   (drop   by
drop)   until   the   bottom   of   the   meniscus   just   touches   the   fill   line.     Insert   the   stopper   and
invert  the  volumetric  flask  several  times  to  insure  that  the  solution  is  thoroughly  mixed.
Determine  the  mass  of  the  stoppered  flask  containing  the  solution  and  record  the  mass  on
the  report  sheet.
After  you  measure  this  mass,  you  may  pour  the  solution  out  of  the  volumetric  flask  (safe  to
pour   directly   down   the   drain).     Rinse   the   flask   several   times   with   deionized   water.     It   is
now   ready   for   the   next   mass   of   sugar   that   you   weigh   out.     Remember,   you   only   need   to
measure   the   mass   of   the   clean,   DRY,   stoppered   flask   once   at   the   beginning   of   the
experiment.    The  flask  does  not  need  to  be  completely  dried  between  solution  preparations,
since  you  will  be  adding  water  to  the  sugar  anyway  to  get  it  dissolved.
Once  the  data  has  been  collected  for  all  five  sugar  solutions,  you  should  turn  your  attention
to   the   soda   that   your   instructor   assigns   for   study.     Use   the   same   volumetric   flask   and
stopper  that  you  used  to  prepare  the  sugar  water  solutions.    Remember,  if  you  use  this
same  glassware,  you  already  know  the  mass  of  the  empty,  dry  stoppered  flask.    Carefully  fill
the   flask   to   the   fill   line   with   flat   soda.     (If   you   are   not   provided   with   flat   soda,   your
instructor   will   give   instructions   for   the   rapid   degassing   of   carbonated   soda.)     Weigh   and
record   the   mass   of   the   stoppered   flask   containing   the   soda.     Your   instructor   will   tell   you
what   to   do   with   the   soda   sample   once   this   mass   has   been   determined.     Repeat   with   a
different  soda  sample  if  your  instructor  wants  you  to  analyze  more  than  one  soda.
Clean  all  glassware,  and  return  it  to  its  proper  location  in  the  lab.

DATA  ANALYSIS
You  should  calculate  the  mass  of  each   sugar  solution  and  soda  sample  by  subtracting  the
mass   of   the   empty   stoppered   flask   from   the   mass   of   the   stoppered   flask   containing   the
solution.     The   density   of   each   solution   can   then   be   determined   by   taking   the   mass   of   the
solution  and  dividing  by  the  solution  volume.    Remember,  when  properly  filled  to  the  mark,
a  100  mL  volumetric  flask  holds  100.0  mL  of  solution  (4  significant  figures).
Using  the  collected  data  and  calculated  results,  construct  a  graph  of  density  (y)  vs.  mass  of
sugar   used   (x).     If   plotting   on   a   computer,   have   the   program   determine   the   best   straight-­‐
3-­‐6
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
line  fit  for  the  data,  and  report  the  equation  for  the  line  on  the  graph.    If  plotting  by  hand,
you   will   have   to   “eyeball”   the   best   straight-­‐line   fit.     Your   instructor   will   discuss   specific
graphing  requirements  for  your  class.
Your   graph   represents   the   relationship   between   the   density   of   the   sugar   water   solution
(which  can  be  determined  experimentally)  and  the  mass  of  dissolved  sugar  in  the  solution
(which  cannot  be  measured  directly  for  the  soda  sample,  because  you  did  not  add  the  sugar
yourself).    There  are  two  ways  you  can  determine  the  mass  of  sugar  in  100.0  mL  of  your
soda  from  your  calibration  curve.    Your  instructor  will  tell  you  which  approach  to  use.
1. Use  the  equation  of  the  best-­‐fit  straight  line,  which  will  be  of  the  form  y  =  mx  +  b,  where
y  =  the  density  of  the  solution,  x  =  the  mass  of  sugar  in  the  solution,  m  =  the  slope  of  the
line,   and   b   is   the   y-­‐intercept.     For   the   soda   sample,   you   know   the   y-­‐value;   use   the
density  of  the  soda  solution  that  you  calculated  from  your  data.    Since  you  did  not  add
the   sugar   to   the   soda,   you   do   not   know   the   x-­‐value.     Solve   for   x   by   rearranging   the
equation.    This  value  represents  the  mass  of  sugar  in  100.0  mL  of  the  soda.
2. If   the   equation   of   the   best-­‐fit   straight   line   is   not   available,   you   will   need   to   estimate   the
mass   of   sugar   as   follows:     Find   the   y-­‐value   that   corresponds   to   the   density   of   your   soda
solution  on  the  y-­‐axis  of  your  plot.    Using  a  ruler,  draw  a  straight,  horizontal  line  from
this  value  to  the  best-­‐fit  straight  line.    At  the  point  where  this  horizontal  line  intersects
the  best-­‐fit  straight  line,  draw  a  perpendicular  (i.e.  vertical)  line  from  the  intersection  to
the   x-­‐axis   (use   a   ruler).     The   x-­‐value   where   this   vertical   line   crosses   the   x-­‐axis
represents  the  mass  of  sugar  in  100.0  mL  of  the  soda.
A  single  can  of  soda  does  not  contain  100.0  mL,  but  rather  12  fluid  ounces  (fl  oz).    To  find
the   mass   of   sugar   in   a   can   of   your   soda,   you   will   need   to   perform   a   unit   conversion
calculation.        A  volume  of  12  fl  oz  is  equivalent  to  355  mL.    Your  instructor  will  tell  you  the
actual  mass  of  sugar  present  in  a  can  of  each  soda  that  is  available  for  analysis.    Compare
your  result  to  the  correct  value  by  calculating  your  percent  error.

SAMPLE  CALCULATIONS
A  student  weighs  an  empty,  dry,  stoppered  100  mL  volumetric  flask  and  finds  the  mass  to
be   65.649   g.     After   3.929   g   of   sugar   is   weighed   out,   all   of   the   solid   is   transferred   to   the
volumetric   flask,   enough   water   is   added   to   completely   dissolve   the   solid,   and   the   flask   is
filled  to  the  mark.    The  mass  of  the  stoppered  flask  containing  the  sugar  water  solution  was
found  to  be  166.89  g.    What  is  the  density  of  the  sugar  water  solution?
(1)   Find  the  mass  of  the  solution.
Mass  of  solution  =  Mass  of  stoppered  flask  +  solution  –  Mass  of  empty,  dry  stoppered  flask
Mass  of  solution  =  166.89  g  –  65.649  g  =  101.24  g

3-­‐7
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
(2)   Calculate  the  density  of  the  solution.
The  volume  of  the  solution  is  100.0  mL.
𝑑 =

101.24  𝑔
𝑚
𝑔
=
= 1.012   𝑚𝐿
100.0  𝑚𝐿
𝑉

WHY  IS  THIS  LAB  GREEN?
All  sugar-­‐water  solutions  and  soda  may  be  poured  directly  down  the  drain.

REFERENCE
J.  Chem.  Educ.,  1999,  76  (10),  p  1411  DOI:  10.1021/ed076p1411

3-­‐8
CHEM  1111
Experiment  3
Name:

Section:                                      Score:
Experiment  3  Prelab  Assignment

1.   A  student  weighs  an  empty  100  mL  volumetric  flask  and  stopper  and  finds  the  mass  to
be   98.595   g.     After   adding  4.163   g   of   sugar   to   the   flask,   dissolving   it,   and   filling   the   flask
to  the  mark,  the  stoppered  flask  is  weighed  again  and  the  mass  is  found  to  be  204.274  g.
Calculate  the  density  of  this  solution.

2.   Explain  how  to  properly  prepare  a  solution  in  a  100  mL  volumetric  flask.

3. Suppose   that   in   adding   water   to   a   volumetric   flask   containing   dissolved   sugar,   you
accidentally   add   too   much   water,   and   the   level   rises   above   the   mark.     You   decide   to
remove   the   excess   water   with   a   pipet,   and   then   you   measure   the   mass   of   the   stoppered
flask   plus   solution.     Explain   why   the   density   calculated   using   this   data   will   not   be
accurate.

3-­‐9
CHEM  1111
Experiment  3
Name:

Section:

Density  (g/mL)

4. A  sample  of  soda  occupying  a  volume  of  100.0  mL  was  found  to  have  a  mass  of  103.87  g.
Use   this   data   and   the   calibration   curve   provided   below   to   determine   the   mass   (in
grams)  of  sugar  in  the  100.0  mL  sample  of  soda.

Density  of  Solution  (g/mL)  vs.  Mass  of  Sugar  (in  grams)

1.06

y  =  0.0038x  +  0.9959

1.05

1.04

1.03
1.02
1.01

1

0.99
0
2
4
6
8
10
Mass  of  Sugar  (g)
3-­‐10
12
14
16
18
CHEM  1111
Experiment  3
Name:

Section:
Score:
Experiment  3  Report  Sheet

Measured  Data:    Be  sure  to  include  UNITS  for  all  measurements.
Your  instructor  will  tell  you  how  many  soda  samples  you  need  to
analyze.
A
B
C
Mass  of  Empty
Mass  of  Sugar
Mass  of  Stoppered

Calculated  Results:    SHOW  WORK  (on  the
back  or  attach  a  separate  page).    Include
UNITS.
D
E
Mass  of  Solution
Density  of  Solution
(Volume  =  100.0  mL  when
flask  is  filled  to  the  mark)
(measure  ONCE  at
beginning)
Sugar  Solution  1

Sugar  Solution  2

Sugar  Solution  3

Sugar  Solution  4

Sugar  Solution  5

Soda  Sample  1

Soda  Sample  2
Soda  Sample  3
N/A

N/A

N/A

3-­‐11

CHEM  1111
Experiment  3
Name:

Section:

Use   the   data   and   results   for   the   sugar   solutions   to   construct   a   graph   of   density   (y)   vs.   mass   of   sugar   (x),   and   fit   the   data   to   a
linear   relationship.     Use   the   graph   paper   provided   on   the   next   page   if   plotting   by   hand,   or   use   a   computer.     If   you   do   use   a
computer,  report  the  equation  for  the  line  on  the  graph.    This  is  your  calibration  curve.    Attach  a  copy  of  your  curve  to  this  report
form.

Use  your  calibration  curve  to  determine  the  mass  of  sugar  in  100.0  mL
of  each  soda  sample  that  you  studied.    Report  your  results  in  the  table  to
the  right.

F
G
H
I

Grams
Calc.
Actual

Sugar  in
Grams
Grams
%  Error

100.0  mL
Sugar  in
Sugar  in

12  fl  oz
12  fl  oz

Soda

Calculate  the  mass  of  sugar  in  a  12  fl  oz  can  of  each  soda  sample.    Report   Sample  1
your  results  in  the  table  to  the  right.    12  fl  oz  =  355  mL
Soda

Sample  2

Soda

Sample
3

Your  instructor  will  provide  you  with  the  actual  sugar  content  in  12  fl  oz
of  each  soda  sample.    Use  this  information  and  your  calculated  results  to
determine  the  percent  error  in  your  results.    Report  your  answers  in  the
table  to  the  right.

3-­‐12
CHEM  1111
Experiment  3
Name:

Section:
Calibration  Curve      (Use  if  Graphing  by  Hand)

Determine  the  range  of  density  values  (max.  value  –  min.  value)    =

Determine  the  value  per  y-­‐axis  division  (range  ÷  40)  rounded  UP    =

Determine  the  range  of  values  for  mass  of  sugar  (max.  value  –  min  value)    =

Determine  the  value  per  x-­‐axis  division  (range  ÷  40)  rounded  UP    =

(Be  sure  to  label  both  axes,  with  UNITS!!!)

Graph  Title:

3-­‐13

Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
Experiment  4
Which  Alkali  Metal  Carbonate?

LEARNING  OBJECTIVES

Learn   how   to   apply   the   Law   of   Conservation   of   Mass   to   a   chemical   reaction,   to
determine  the  mass  of  a  product  formed
Learn  how  to  calculate  the  molar  mass  of  an  unknown
Learn   how   to   identify   a   compound   based   on   its   experimentally   determined   molar
mass

INTRODUCTION
Imagine   you   are   an   analytical   chemist   and   have   received   a   sample   of   a   pure   alkali   metal
carbonate  from  a  newly  discovered  deposit.    Your  task  is  to  determine  which  alkali  metal
carbonate  is  present  in  the  sample.    You  will  determine  an  experimental  molar  mass  for  the
alkali   metal   in   the   carbonate   and,   from   that   result,   you   will   determine   which   alkali   metal   is
present.
To   identify   your   unknown,   you   will   employ   the   Law   of   Conservation   of   Mass.     This   law
states  that  in  a  chemical  reaction  the  total  mass  of  the  reactants  must  equal  the  total  mass
of  products.
Alkali   metal   carbonates   (X2CO3)   react   with   HCl   according   to   the   following   equation   (X   is
meant  to  represent  the  unknown  alkali  metal  cation):
𝑋! 𝐶𝑂! 𝑠 +    2  𝐻𝐶𝑙 𝑎𝑞   →    2  𝑋𝐶𝑙 𝑎𝑞   +     𝐶𝑂! 𝑔 +     𝐻! 𝑂(𝑙)                                            (1)
Note   that   one   of   the   products   (CO2)   is   a   gas.     If   the   reaction   is   performed   in   an   open   vessel,
this  gaseous  product  will  escape  as  the  reaction  proceeds  to  completion.    The  mass  of  CO2
generated  can  be  calculated  if  the  mass  of  the  reactants  used  is  known  accurately,  and  the
mass  of  the  reaction  mixture  at  the  end  of  the  reaction  is  also  known.
Mass  of  CO2  =  [mass  of  X2CO3(s)  +  mass  of  HCl(aq)]  –  (final  mass  of  reaction  mixture)                                    (2)
Using   dimensional   analysis,   the   mass   of   CO2   can   be   converted   to   moles   of   CO2   using   the
molar   mass   (ℳ)   of   CO2   as   a   conversion   factor.     The   molar   mass   of   CO2   is   calculated   by
adding   together   the   atomic   weights   of   all   of   the   atoms   in   the   molecule:     1   C   atom   (12.01
g/mol)  plus  2  O  atoms  (2  x  16.00  g/mol)  =  44.01  g/mol.

𝑔𝑟𝑎𝑚𝑠  𝐶𝑂!
ℳ!”!
𝑚𝑜𝑙𝑒𝑠  𝐶𝑂!                                                                                                      (3)
The  number  of  moles  of  CO2  is  related  to  the  number  of  moles  of  the  alkali  metal  carbonate
(X2CO3)  by  the  coefficients  in  the  balanced  chemical  equation  (Equation  1,  written  above).
This   equation   indicates   that   1   mole   of   CO2   will   be   produced   for   every   1   mole   of   X2CO3
consumed  in  the  reaction.
4-­‐1
Austin  Community  College
CHEM  1111  –  General  Chemistry  I  Lab
𝑚𝑜𝑙𝑒𝑠  𝐶𝑂!
!  !”#  !”!  !    !  !”#  !! !”!
𝑚𝑜𝑙𝑒𝑠  𝑋! 𝐶𝑂!
(4)
Once  the  number  of  moles  of  X2CO3  has  been  determined,  the  molar  mass  can  be  calculated
using  the  definition  of  molar  mass:
𝑀𝑜𝑙𝑎𝑟  𝑚𝑎𝑠𝑠 =
!”#\$%  !”  !”#\$”%&’
!”#\$%  !”  !”#\$”%&’
(5)
Finally,   after   the   molar   mass   of   X2CO3   has   been   calculated,   the   molar   mass   of   the   alkali
metal  atom  X  can  be  determined,  and  the  unknown  metal  can  be  identified:
𝑀𝑜𝑙𝑎𝑟  𝑚𝑎𝑠𝑠  𝑋! 𝐶𝑂! = 𝑠𝑢𝑚  𝑜𝑓  𝑚𝑜𝑙𝑎𝑟  𝑚𝑎𝑠𝑠𝑒𝑠  𝑜𝑓  𝑎𝑙𝑙  𝑎𝑡𝑜𝑚𝑠  𝑖𝑛  𝑡ℎ𝑒  𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑

=  2(ℳ  of  X)  +  ℳ  of  C  +  3(ℳ  of  O)
(6)

The   “Sample   Calculations”   section   below   provides   examples   of   how   to   use   Equations   2
through   6   to   complete   the   calculations   that   you   will   need   to   perform   once   you   collect   your
data  for  Part  A  of  the  procedure.
An   alternative   approach   for   identifying   the   unknown   requires   that   the   volume   of   HCl
solution  required  to  react  completely  with  the  X2CO3  be  measured  very  accurately.    For  this
strategy  to  work,  knowledge  of  the  molarity  of  the  HCl  solution  is  also  required.    Molarity
is  a  common  way  to  describe  the  concentration  of  a  solution.    It  is  defined  to  be  equal  to
the  moles  of  solute  divided  by  the  volume  of  the  solution,  expressed  in  units  of  liters:
𝑀𝑜𝑙𝑎𝑟𝑖𝑡𝑦  𝑜𝑓  𝐻𝐶𝑙 𝑎𝑞 =
𝑚𝑜𝑙𝑒𝑠  𝐻𝐶𝑙

𝑙𝑖𝑡𝑒𝑟𝑠  𝑜𝑓  𝐻𝐶𝑙  𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛
(7)
If  the  volume  of  HCl  solution  of  known  molarity  required  to  react  completely  with  a  sample
of  X2CO3  is  measured  very  carefully,  rearrangement  of  Equation  (7)  allows  for  the  number
of   moles   of   HCl   consumed   in   the   reaction   to   be   calculated.     The   coefficients   in   the   balanced
chemical   equation   (1)   can   then   be   used   to   determine   the   number   of   moles   of   X2CO3   that
reacted  with  the  HCl:
…

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