Weak Diprotic/Dibasic Acid-Base Titration Curve

DiproticAcid-BaseTitrationlabreportrubric-Fall20191 lab6data.csvLab6data.cmblAcid-basetitrationcurveofdiproticweakacids-bases1

Weak Diprotic/Dibasic Acid-Base Titration Curve

CHEM 3221 Quantitative Chemical Analysis Lab
Lab Report Rubric

Name: Total Points:

SafeAssign: Yes No (Zero points if not submitted) Number of Days Late (10% off per day) days

Important Note:
– Entire report should be typed. Any handwritten part (excluding calculation work) will not be graded.
– Zero points on the lab report sections for non-original writings detected by SafeAssign.

Weak Diprotic/Dibasic Acid-Base Titration Curve

1. Title and Title Page ____ (5)
a. Descriptive title clearly stating what was/were performed
b. Author’s name and lab partner (if any) following the title on a separate line

INSTRUCTOR’S COMMENTS:

__________________________________________________________________________________________________

2. Abstract (100 – 150 words) ____ (5)
a. Briefly state the purpose of the study
b. Indicate the experimental plan (2 – 3 sentences)
c. Key results (Kb1 and Kb2, molar mass, and identification of the unknown base sample. No statistical results needed)
d. Major conclusions (1 – 2 sentences)

INSTRUCTOR’S COMMENTS:

3. Introduction _____ (15)
a. Clear statement of the objective and why you are performing the titration
b. Write two-step balanced chemical equations of the neutralization reaction involved in the titration: use general

formula, B for the dibasic base and indicate the dissociation constants (expression not needed) for each ionization step
c. Describe briefly in 3 – 4 sentences how the Vernier unit and pH probe were used in data collection
d. Describe clearly the different regions of the titration curve and how the pH changes in the course of the titration:

indicate the buffer regions, two half-equivalence points, and two equivalence points
e. Explain where the equivalence points are located in the sigmoidal curve and how do you determine the equivalence

points from the titration curve
f. Describe how the half-equivalence point volumes and the corresponding pH, and finally pKb1 and pKb2 are determined

from the titration curve
g. Describe briefly how the molar mass (MW) of the unknown dibasic base is calculated from the equivalence point
h. Write the formulas/calculation steps used for calculating pKb1, pKb2, Kb1, and Kb2, and the molar mass of the unknown

dibasic base

INSTRUCTOR’S COMMENT:

____

_________________________________________________________________________________

4. Materials and Methods _____ (12)

a. Description of apparatus, equipment and instrumentation with capacity and tolerance as applicable
b. Do not include a list as in a recipe
c. Chemical names, source, and purity of the chemicals used
d. Describe any hazards in a separate paragraph with a heading “Caution:” Include precautionary handling procedures,

special waste disposal procedures, and any other safety considerations for each chemical in adequate detail.
e. Description of experimental methods in sufficient details (past tense, third person, passive voice) in your own words

that anyone would be able to follow your procedures and repeat your experiment including calibration and Vernier
LabQuest/pH probe setup and operation steps

INSTRUCTOR’S COMMENT:
__

_______________________________________________________________________________

5. Data Collection _____ (3)
a. Data collected directly into lab notebook in organized tables recorded to the maximum precision of the instrument

(indicator titration data only)
b. Original copy signed and clear carbon copy data pages submitted at the end of lab period

INSTRUCTOR’S COMMENT:
_______________________________________________________________________________

6. Results _____ (15)
a. Tabulation of experimental data, results, and statistical treatment clearly and concisely. Use proper titles, units and

significant figures for data and results in a logical sequence

i. Insert Table of experimental data and results in sequence w/ proper format, units, significant figures, and
subscripts.

ii. pH vs. volume LoggerPro printed titrant data (no separate data table needed)
iii. Sigmoidal graph, and first or second derivative curve (enlarged to full page) from the Logger Pro or Excel

program
iv. Label two equivalence points, two half-equivalence points, and the corresponding volumes and pH clearly on

the first/second derivative graph by drawing reference lines on horizontal and vertical axes and record each
volume and pH in your data table

v. Include Volume and M of HCl (previously standardized) in your data table
vi. Identify and label the pKa1 and pKa2 on the second derivative graph

vii. Calculate Kb1 and Kb2 of unknown base from above pK1, and pK2 values and record in your data table
viii. Calculate number of moles of unknown base titrated and record in your data table

ix. Calculate molar mass of the unknown dibasic base sample and record in your data table

INSTRUCTOR’S COMMENT:

_____________________________________________________________________________________

7. Discussion _____ (10)
a. Relate your result to the original purpose of the experiment

i. What did you find out from your results: Was the problem resolved? What has been contributed?
b. Identify sources of errors

i. Mention whether each error is systematic or random error
ii. Predict the effect of each error source on the final results (M NaOH value)
iii. Describe ways to minimize each error
iv. Errors due to carelessness, wrong procedure, miscalculations etc. are not acceptable errors