Central Washington University Preparation of Buffers and pH Lab Report

Name: Bader AlshammariClass: BCH 381_006
Assignment: Pre-lab
Determining pH and Making Buffers
Introduction:
The pH, which means potential hydrogen, known as the measure of the hydrogen ion
concentration, exists in a solution. The more the hydrogen ions dissociate in a solution, the
stronger the acid. Therefore, the solution will be more acidic. The pH ranges from 0, the most
acidic, to 14, where the solution becomes most alkaline or basic. On that scale, at pH equals 7,
the solution becomes natural, which means the hydrogen and hydroxide ion concentrations are
equal, and the solution is neutral. The basic equation for calculating the hydrogen concentration
in a solution is pH= -log [H+]. The human body contains cells and amino acids that must operate
at a certain pH level. Thus, if that pH was disturbed to reach a different value than the optimal
pH, a malfunction could lead to alkalosis or acidosis and eventually death. The skills of
measuring the pH are crucial for becoming a biologist, and they are essential for people who test
human blood at the laboratory. A commonly known method of measuring the pH of a solution is
using the titration curves where a buffer system is introduced by adding the hydroxide ion to a
weak acid to form its conjugate base, and an example of that would be NaH2PO4 which
represents the weak acid and its conjugate base Na2HPO4. That buffer system can resist changes
in pH when adding hydrogen or hydroxide ions with a one PH value range at the solution’s pKa
value. Buffering results from two reversible reaction equilibria occurring in a solution of nearly
equal concentrations of a proton donor and its conjugate proton acceptor (Nelson et al., 2017).
The human body also contains a carbonic acid/bicarbonate buffer in the blood. The carbonate
buffer could maintain the pH level at the expected value in the blood when rejecting changes in
the pH. The purpose of this experiment is to determine the pH value of a solution and make
buffers to resist any changes due to the addition of hydrogen and, or hydroxide ions. The
Henderson-Hasselbalch equation: pH= pKa +log[A-]/[HA] relates pH, pKa, and buffer solution
concentration where it is handy to calculate one variable when given the other two variables.
References
Nelson, D. L., Cox, M. M., & Lehninger, A. L. (2017). Lehninger principles of biochemistry.
W.H. Freeman.
“Please follow the rubric precisely”
Sample Lab Report Rubrik:
(100pt lab report total)
1. Title or Cover Page (5pts)
Give content information
Give contact information
Exceptional
Engaging experiment title
Acceptable
Appropriate experiment title
Includes name, lab partner,
section info, semester
Missing collaborators or
laboratory section info
Unacceptable
Title not descriptive or
much too long
Key information missing
2. Purpose / Introduction (15pts)
Exceptional
Provide appropriate
background information
Identify central
experimental questions
Present a hypothesis and
a means of testing it
#1 Background information is
presented in an engaging
manner
#2 Experimental goals and
predictions are clear
#3 Key Reagents and Concepts
are Explained in sufficient
detail
#4 Hypothesis is a logical
extension of existing
knowledge
Acceptable
#1 Background information is
presented but could be
reorganized
#2 Experimental goals are
unclear
#3 Reagents and concepts
are mentioned, but
explanations are
unclear/incomplete
#4 The reader can connect
your hypothesis to
background information
with some effort
Unacceptable
#1 Background information
is too general, too
specific, missing and/or
misrepresented
#2 Experimental question is
incorrectly identified or
not identified
#3 Key Reagents not
mentioned, concept of
experiment not explained
#4 No plausible hypothesis
or reasoning is given
3. Experimental Methods (10pts)
Exceptional
Include a correctly
formatted citation of the
lab manual
Describe procedures
correctly, clearly, and
succinctly
Include any major
equations used
(if applicable)
#1 Lab manual cited
Acceptable
#1 Lab manual citation is
incorrectly formatted
#2 Sufficient detail for
another researcher to
repeat your experiment;
All changes to procedure
are clearly explained
#2 Procedures could be
pieced together with
some effort;
Most changes to
procedure are given
#3 Equations are all correct
and defined
#3 Equations are present,
but missing key
information
Unacceptable
#1 Lab manual not cited
#2 Procedures are incorrect,
unclear, or missing
#3 Key equations are
incorrect or missing
4. Results (25pts)
Exceptional
#1 Text and figures present
data clearly and are easy to
understand
Present your data using
text AND figures/tables
#2 Text and figures are
logically organized and
referenced in the narrative
Provide a narrative
linking experimental
results
#3 Figures and tables contain
all relevant information
and are easy to interpret
#4 All figures and tables have
numbers, titles and
legends that allow for clear
interpretation of the data
Acceptable
#1 Text and figures could be
reworded \ reformatted
or suffer from incorrect
scientific language
#2 Text includes
interpretation of results
that is better suited for
discussion section or is
not logically organized
#3 Figures and tables are
formatted properly but
missing key information
#4 All figures and tables
allow for adequate
interpretation of the data
Unacceptable
#1 Text omits key findings,
inaccurately describes
data, or includes
irrelevant information
#2 Text is difficult to read
due to style, or due to
logic / organization
#3 Figures are improperly
constructed or cannot be
understood due to lack of
information
#4 Figures and tables have
inadequate or missing
titles or legends
5. Discussion (30pts)
Exceptional
#1 Appropriate conclusions
are drawn from results
#2 Evidence for conclusions
are presented clearly and
correctly from results
Provide a narrative
interpreting
experimental results
Evaluate meaning and
importance of major
findings
#3 Inconsistencies and errors
are clearly addressed and
their impact on the
experiment is considered
#4 Writing is compelling:
logical, well organized, and
easy to understand
#5 Experimental findings and
limitations are considered
for future direction
Acceptable
#1 Some conclusions are
drawn from results
#2 Conclusions are given
insufficient support
Unacceptable
#1 Conclusions omitted,
incorrectly drawn or not
related to hypothesis
#2 Conclusions contradict
experimental findings
#3 Experimental limitations
are not considered or
impact on experiment is
poorly addressed
#3 Experimental limitations
missing, incorrectly
addressed, or dismissed
#4 Writing is understood but
is disorganized or
presented illogically
#4 Writing makes argument
difficult to follow or
undermines conclusions
#5 Conclusions are
summarized for future
experiments
#5 No final conclusions are
given for the experiment
6. References (5pts)
Exceptional
Give credit on which
your own work is based
Use ACS style format
Acceptable
#1 Multiple reliable sources
(e.g. peer-reviewed journal
articles)
#2 Properly formatted both in
body of report and in
reference section
#1 Some sources are not
cited or unreliable
#2 With minor exceptions,
properly formatted in
body of report and in
reference section
Unacceptable
#1 References missing or do
not correlate with in-text
citations found in report
#2 References not properly
formatted or citations
missing in body of report
7. Style (10pts)
Acceptable
Unacceptable
Appropriate for audience
Too simple or too advanced
Consistent use of passive voice
Irregular use of passive and active voice
Concise
Verbose
Says what you mean
Ambiguous or incorrect
Scientific vocabulary used correctly
Scientific vocabulary misused
#1 Voice
#2 Word Choice
Sentences and paragraphs well
structured
#3 Fluency
Punctuation correct or only minor
errors
Grammar correct or minor errors
Sentences repetitive or awkward;
Paragraphs not used or not logical
Periods, commas, colons and semicolons
misused
Significant number of run-on sentences,
sentence fragments, misplaced
modifiers, subject/verb disagreements
Spelling correct
Significant number of spelling errors
Past tense for describing new findings
Present tense used for accepted
scientific knowledge and figure legends
#4 Scientific Format
All sections included and properly
formatted
Descriptive legends and captions for
figures and table
Units are given for all quantities and
are correctly formatted
Misleading verb tenses
Some sections missing
Figures missing legends or captions
Units are not given for all quantities or
are incorrectly formatted
Your TITLE needs to clearly and concisely describe the emphasis and topic
of your report
Your Name; Partner Name; TA Name. Your name is listed first, designating the author. Contributors are separated by semicolons. Use first names, initials, and surnames (e.g., John R. Smith) or first
initials, second names, and surnames (e.g., J. Robert Smith). Do not use only initials with surnames
(e.g., J. R. Smith).
SECTION INFORMATION. Write your university, the date you submitted your report, as well as your class and section.
(e.g. Montana State University, Fall 2019, BCH 380 Section 002)
Introduction
Provide background information leading up to your hypothesis. Explain why this would be interesting to the scientific
community. Include any ideas or techniques that are necessary to understand the results section, using figures if necessary. Cite references to frame the relevance of the experiment. Make a prediction based on the background information you provided and frame a hypothesis.
Experimental Methods
Provide succinct procedures using scientific language. Much like a recipe, quantities, time, etc. need to be recorded, but
not e.g. glassware used. Enough detail must be included so that any researcher can repeat your experiment and have
the same results. Procedures must be written in complete sentences, using paragraphs to delineate major intermediates. This section is written in past tense, since all experiments are completed at the time of writing.
Any major equations used are typically found in this section. Equations are numbered sequentially, and the terms of
the equation are defined the first time they appear. (It is not necessary to redefine a term every time it appears in an
equation.) Any terms used must be consistent throughout the text.
If following an established procedure, the original source must be cited. Any major deviation from the procedure must
be clearly identified.
Example: Procedures were followed with minor modifications according to Schlick, K. Biochemistry 380 Lab Manual;
Montana State University: Bozeman, MT, 2019.
Measurements were taken using a GENESYS 50 UV-Vis Spectrophotometer. The concentration of the L-DOPA substrate was changed to 2 mg/mL, and volumes were adjusted as outlined in Table 1. Briefly: the concentration of the
experiment’s mushroom tyrosinase was obtained using absorbance. Kinetic data were obtained by adding aliquots
of L-DOPA to a known enzyme solution and recording the changes in absorbance.
Results
This section presents your data in a clear and easy to understand format. Organize your data in figures and tables, which
include descriptive captions for each. Ideally, most of the experiment’s outcome can be deduced from the organization
of figures and tables alone. Interspersed with your figures and tables, your major points need to be organized in paragraphs, referencing your data as necessary.
The narrative of this section does not interpret data! It is a “no judgement” display of findings. Include your complete
findings, even the results that may not make immediate sense.
Discussion
In this section, the implications of the results section are discussed. The data is interpreted, demonstrating your understanding. The discussion section of a scientific report should be objective. Use a paragraph for each major conclusion drawn from the data, introducing new figures as necessary to strengthen your argument. Evidence for each statement needs to be included by referring to your data or citing a reference.
A strong discussion needs to address any inconsistencies or limitations found during the experiment. If possible, explain how your data relate to what others have found. Major errors need to address how these may have impacted the
results of the experiment. Note: “human error” is not an acceptable source of error! Systematic error arises from experimental design, due to e.g. instrumentation or failing to account for a factor. Random error is a statistical variation,
due to e.g. environmental factors or reading a meniscus incorrectly (parallax).
The conclusion of the discussion section often summarizes your final findings in a few sentences. Future directions
and experiments are often considered, based on the outcome of the experiment.
References
References are listed in order that they appear in the report, with corresponding numbers. These are given in a format consistent with the ACS style guide.
Example: 1. Dalton, H.R; Nelson, J.M. Tyrosinase from the Wild Mushroom, Lactarius Piperatus. J. Am. Chem. Soc.
1939, 61, 2946-2950.
Style tips:
•
“Read” the report by scanning the figures in order. The figures should provide a self-explanatory overview of
your data, using legends and captions. Decide what the data show, then create figures which highlight the
most important points of your paper.
•
Use figures to present numerical trends, raw data (like a picture of a gel), or a model that explains your work.
Use tables to present numerical, repetitive data. Don’t forget to include units!
•
All tables and figures must be numbered and have explanatory captions. Captions should allow the reader to
understand the data without reading the text. Don’t forget axis labels for graphs. Include titles and legends as
necessary.
•
Avoid making tables too large. It may be better to produce two separate tables and address each individually.
•
Avoid ineffective tables. Some information is better presented in one or two sentences.
•
Procedures and results are written generally in passive voice, to avoid personal bias and emphasize objectivity. This also stresses that the experimental outcome should not depend on the observer.
•
Do not write procedures as directions! E.g. “Heat the solution until it boils” is not acceptable. Instead, use
“The solution was heated to boiling.”
•
The results section is written in past tense, since it is an account of you did in your experiment. Established
scientific knowledge is written about in the present tense.
o Example: “[…] was seen (Figure 3).” or “”The world is round.”
•
The discussion section is often written in present tense, as it reflects your current conclusions from the data.
o Example: “Figure 3 suggests that […]“
•
Include reference numbers in your report using a superscript. Write out corresponding full citation at the end
of the report formatted according to the ACS style guide.
Descriptive Title for the Experiment
John Author; Jane Partner; Thomas Helper
Montana State University, Fall 2019, BCH 380 Section 002
Introduction
Provide background information relevant to your experiment.1 Explain any techniques that need to be understood in order
to evaluate the data.2 Include 1-3 references.
Outline your experimental goals.
Outline your hypothesis.
Experimental Methods
Procedures were followed with minor modifications according to Schlick, K. Biochemistry 380 Lab Manual; Montana
State University: Bozeman, MT, 2019.
Outline any changes to the BCH 380 lab manual you did.
Calculation of [e.g. enzyme concentration]
[E.g. enzyme concentration] was calculated by applying [ e.g. Beer’s Law] to results found in [Table 1].
Equation 1:
Enter your formula corresponding to the calculation.
[Define your parameters for Equation 1]
Results
Summarize what you found from your initial data. Provide a narrative that clarifies the findings of your first figure or
table. Do not interpret your data, only present it!
Insert your first figure/table here. This must be clear enough such that the reader can
draw their own conclusions from the data. Include a caption below the figure.
Figure 1. [Short description of the figure]
Present your second batch of findings.
Insert your next figure or table.
Table 1. [Short description of the table]
Continue the above as necessary to present your complete data. Even include results that may not make sense initially,
as the next section will deal with interpreting them.
Discussion
The discussion section discusses the implications of your results section. Summarize your major findings.
Demonstrate your understanding of the results. As a general rule, prove any assertion by citing your data or a reference. 3
Discuss any inconsistencies or limitations found. Address any major errors and their impact on the outcome of the experiment.
Conclude your discussion with a summary of your final findings. Consider future directions or relevance based on the
outcome of your experiment.
References
1. [Reference corresponding to (1) above]
2. [Reference corresponding to (2) above]
3. [Reference corresponding to (3) above]