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CHEM 152 lab 2_Buffers Report Complete -Graded A
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CHEM 152 lab 2_Buffers Report Complete -Graded A
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NAME: QUIZ SECTION: ACSTUDENT ID: LAB PARTNER:
Chem 152 Lab #2: Buffers Note:
All sections of this
Total Points = 60 pts (10 notebook, 50 template) report must be typed
By signing below, you certify that you have not falsified data, that you have not plagiarized any part of this lab report, and that all calculations and responses
other than the reporting of raw data are your own independent work. Failure to sign this declaration will result in 5 points being deducted from your lab score.
Signature:
Deprotonation of Acetic Acid 3 pt rxn, 2 pt for Ka, 2 pt for Kb (correct & entered)
Provide the Ka Provide the Kb value for the
Provide the acid dissociation reaction for proton removal in water: value for the acid conjugate base
CH3COOH(aq) + H2O (l) <=> CH3COO- (aq) + H3O+ (aq) 1.8E-05 Kb=Kw/Ka =5.56E-10
DATA AND CALCULATIONS
Parts A - D: Preparation of Acetic Acid/Acetate Solutions 5 pts: ALL solution prep data and expected initial pH values entered
Molarity of Stock
Soln
(M)
CH3COOH 0.1M
Molar Mass Mass of Solid Moles of Solid Volume of Water *Molarity
(g/mol) Used (g) (mol) (mL) (M)
CH3COONa·3H2O 136.08 g/mol 1.361g 0.01 mol 100mL 0.1M *(from calculation on pg 2)
*Summary of
Expected Initial
Solution ID mL of CH3COOH mL of CH3COONa mL Water Total Volume pH
#1 20.00mL 0.00mL 30.00mL 50.00mL 3.07 *(based on example
#2 15.00mL 5.00mL 30.00mL 50.00mL 4.27 calculations on pg 2)
#3 10.00mL 10.00mL 30.00mL 50.00mL 4.74
#4 5.00mL 15.00mL 30.00mL 50.00mL 5.22
#5 0.00mL 20.00mL 30.00mL 50.00mL 8.67
DI Water -- -- 50.00mL 50.00mL 7.00
Part E: Preparation of Aspirin and Buffered Aspirin Solutions
Mass of Solid Mass of Solid (for
(for acid test) base test)
(g) (g)
Aspirin 0.218g 0.214g Molarity of HCl for acid test: 0.5M Molarity of NaOH for base test: 0.5M
Buffered Aspirin 0.433g 0.431g Volume (mL) of HCl added: 0.25mL Volume (mL) of NaOH added: 0.25mL
Millimoles of HCl added: 0.125mmol Millimoles of NaOH added: 0.125mmol
Parts C-E: pH Measurements and Determination of Buffer Capacity 5 pts: ALL pH values and calculated buffer capacities entered
Buffer
pH Measured Capacity
Initial Measured pH Measured *Buffer Capacity (mmol H+ Initial Measured After OH- (mmol OH-
Solution ID pH After H+ Addition added /DpH) Solution ID pH Addition added /DpH)
#1 3.10 2.35 0.20 #1 3.15 3.89 0.17
#2 4.22 3.79 0.29 #2 4.19 4.34 0.83
#3 4.61 4.35 0.48 #3 4.60 4.86 0.48
#4 5.10 4.71 0.32 #4 5.15 5.47 0.39
#5 7.14 5.58 0.080 #5 6.93 11.51 0.027
DI Water 7.58 2.23 0.023 DI Water 8.07 11.42 0.037
Aspirin (acid) 2.86 2.35 0.25 Aspirin (base) 2.75 3.15 0.313
Buffered Aspirin (acid) 5.81 4.73 0.12 Buffered Aspirin (base) 5.89 7.64 0.714
*example calculation for Solution #2 buffer capacity is on pg 3
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