CHEM 201
Discussion Worksheet 2
Summer 2022
Instructions for Working out the Worksheets:
Work in groups of 4 on these problems. You should try to answer the questions without referring
to your textbook. If you get stuck, try asking another group for help. Your TA will come around
when needed to help guide you if needed.
Round Robin Instructions:
1. Each group member will be assigned a number, starting with #1 and ending with the number
of people in the group.
2. Student #1 will read the question aloud and define the information needed to solve the
problem, create an outline on how you can solve the problem.
3. When the group agrees that the necessary information is complete, student number two will
do the first mathematical step. When the group agrees that the step is correct, student
number three will do the next step. Continue this way until the group agrees that the given
answer had been correctly converted to the wanted answer.
4. Student #2 will start the next question by reading it aloud as in #1. Follow this pattern for all
the questions in the session.
Topics being Covered in the Worksheet:
1. pH, pOH, [H3O+], [OH—]
2. Relative Strengths of Acids and Bases
3. Hydrolysis of Salts
4. Buffers
5. Titration Curves
1 – 4 In the following problems you will be solving mathematical problems to help you
understand topic 1. Make sure you have the correct significant figures for each problem.
1. What is the pH of a 0.0235 M H2SO4 solution?
2. What is the pOH of a 0.0235 M H2SO4 solution?
3. A solution is created by measuring 3.60 x 10–3 moles of Ba(OH)2 in 1000 mL container. What
is the pH and pOH of this solution?
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CHEM 201
Discussion Worksheet 2
Summer 2022
4. Fill in the following table:
pH
pOH
[H3O+]
[OH—]
Acidic, Basic, or
Neutral
4.567
Neutral
2.9 x 10–5 M
5.63452
3.4567 x 10–9 M
5 — 8 In the following problems you will be relating Ka and Kb values to understand the acid
base strengths to help you understand topic 2. Make sure you have the correct significant
figures for each problem.
5. Fill in the following table:
Compound:
pKa
pKb
Ka
A
Kb
2.54 x 10–4
5.621
B
1.74
C
8.9647 x 10—6
D
6. Rank the above compounds in increasing stronger acids.
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CHEM 201
Discussion Worksheet 2
Summer 2022
7. Rank the above compounds in increasing stronger bases.
8. Write out the acid or base dissociation of the following compounds:
(a) CH3OH (acid)
(b) C8H10N4O2 (base)
9 In the following problems you will be identifying the salt as either acidic, basic, or neutral to
help you understand topic 3. Make sure you have the correct significant figures for each
problem.
9. Identify the following acids as acidic, basic, or neutral:
(a) FeCl3
(b) K2CO3
(c) NH4Br
(d) KClO3
10 — 12 In the following problems calculate and identify buffers to hep you understand topic 4.
Make sure you have the correct significant figures for each problem.
10. What is [H3O+] in a solution of 0.075 M HNO2 and 0.030 M NaNO2? Ka = 4.5 x 10—5
11. What is the [OH—] in a solution of 0.125 M HCH3NH2 and 0.130 M CH3NH2Cl?
Kb = 4.4 x 10—4
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CHEM 201
Discussion Worksheet 2
Summer 2022
12. Identify if the following are buffers or not and explain why or why not.
(a) HI/NaI
(b) NH4Cl/NH3
(c) KCH3CO2/CH3CO2H
(d) Na2HPO4/KPO4
13 — 14 In the following problems calculating titration curves to hep you understand topic 5.
Make sure you have the correct significant figures for each problem.
13. Calculate the pH of the following points in a titration of 30.00 mL of 0.200M propionic acid
CH3CH2CO2H Ka = 1.34 x 10–5 with 0.200M NaOH.
(a) no NaOH added
(b) 10.00 mL of NaOH added
(c) 25.00 mL of NaOH added
(d) 30.00 mL of NaOH added
(e) 35.00 mL of NaOH added
(f) 45.00 mL of NaOH added
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CHEM 201
Discussion Worksheet 2
Summer 2022
14. Calculate the pH of the following points in a titration of 50.00 mL of 0.100M KOH with
0.100M HBr.
(a) no HBr added
(b) 10.00 mL of HBr added
(c) 25.00 mL of HBr added
(d) 50.00 mL of HBr added
(e) 55.00 mL of HBr added
(f) 65.00 mL of HBr added
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