Acid Base Chemistry and Buffers Concept Tests
Problem 1
A comic book villain is holding you at gun point and is making you
drink a sample of acid. She gives you a beaker with 100ml of a strong acid
with pH=5. She also gives you a beaker of a strong base with a pH=10. You
can add as much of the strong base to the strong acid as you want, and
you must then drink the solution. You’d be best off trying to make the
solution neutral before drinking it. How much of the base should you add?
A. 1 ml
B. 10 ml
C. 100 ml
D. 1000 ml
Problem 2
Consider an exceptionally weak acid, HA, with a Ka = 1x10 -20
. You make a 0.1M solution of the salt NaA. What is the pH?
A. 1
B. 2
C. 12
D. 13
Problem 3
You have a powder that dissolves in water to form a strong acid.
You dissolve 2g of the powder in 100ml of water, and measure the pH to
be 4. You would like to form 100ml of a solution with pH 5. How many grams
of the powder do you dissolve in 100ml of water?
A. 0.2 g
B. 0.4 g
C. 20 g
D. 40 g
Problem 4
You have two solutions, both with a concentration of 0.1M. Solution
A contains a weak acid with a pKa of 5. The pH of solution A is 3. Solution
B contains a weak acid with a pKa of 9. The pH of solution B is:
A. 1
B. 2
C. 4
D. 5
Problem 5
You have 50 ml of a complex mixture of weak acids that contains some HF (pKa = 3.18)
and some HCN (pKa = 9.21). Which is larger, [F-]/[HF] or [CN-]/[HCN]?
A. [F-]/[HF]
B. [CN-]/[HCN]
C. can.t tell from available information
Problem 6
A mixture of 50ml of 0.1M HCOOH and 50ml of 0.05M NaOH is equivalent
to:
A. a 0.05M solution of NaCOOH
B. a 0.025M solution of NaCOOH
C. a solution that is 0.05M in HCOOH and 0.05M in NaCOOH
D. a solution that is 0.025M in HCOOH and 0.025M in NaCOOH
Problem 7
I want to make a solution that will have [HCOO - ] = 3[HCOOH]. I
start with 100ml of a 0.1M HCOOH solution. How many ml of a 1M KOH
solution should I add?
A. 5ml
B. 7.5ml
C. 25ml
D. 75ml
Problem 8
Which do you think is a better buffer (more resistant to addition
of acid and base)?
A. a solution that is 0.1M in HA and 0.01M in A
B. a solution that is 0.01M in HA and 0.1M in A
C. a solution that is 0.1M in HA and 0.1M in A
D. a solution that is 0.05M in HA and 0.05M in A
Problem 9
Consider a protein with the acidic side chains,
Amino Acid
side-chain
Arginine
pKa = 12.48
Aspartic Acid
pKa = 3.90
Cysteine
pKa = 8.33
Glutamic acid
pKa = 4.07
Histidine
pKa = 6.04
Lysine
pKa =10.79
Tyrosine
pKa =10.13
Given that the pH of blood is about 7.3, how many of the above side
chains would be mostly in their ionic form (A-) in blood?
A. 2
B. 3
C. 4
D. 5
Problem 10
You are titrating an acid with a pKa of 7. You are given a choice
of indicators with the following pKa’s,
A. 3 B.
5
C. 7 D. 9
Which do you use?
Problem 11
CO2 dissolves in water to form carbonic acid:
H2CO3 <---> H+ + HCO3-
Ka1 = 4.3 x l0-7
HCO3- <---> H+ + CO3-2
Ka2 = 4.8 x l0-11
In an acid solution with pH =4.35 ([H+ ]=4.5x10-5),
what is the ratio [CO3-2] / [H2CO3]?
A. 10-2
B. 10-4
C. 10-6
D. 10-8
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