Question 1
Which of the following best describes the significance of Ka in the context of acids?
A. It represents the concentration of the acid.
B. It indicates the strength of a base.
C. It is the acid dissociation constant, indicating the strength of an acid.
D. It represents the pH of the acid solution.
Question 2
A weak acid has a Ka value of 1 x 10^-5. What can be inferred about its strength?
A. It is a very strong acid.
B. It is a moderately strong acid.
C. It is a weak acid.
D. It is a very weak acid.
Question 3
Which of the following is true about the mechanism of buffer action?
A. Buffers resist changes in pH by neutralising added acid or base.
B. Buffers increase the pH of a solution.
C. Buffers decrease the pH of a solution.
D. Buffers have no effect on pH.
Question 4
Which of the following is NOT a characteristic of a strong acid?
A. It completely ionises in water.
B. It has a high pH value.
C. It has a high value of Ka.
D. It donates protons readily.
Question 5
What is the relationship between Ka and Kb for a conjugate acid-base pair?
A. Ka x Kb = Kw
B. Ka + Kb = Kw
C. Ka - Kb = Kw
D. Ka / Kb = Kw
Question 6
a) Define Ka and explain its significance in determining the strength of an acid. [3]
b) A weak acid, HA, has a Ka value of 1.8 x 10^-5. Calculate the degree of ionisation if the concentration of HA is 0.1 M. [2]
Question 7
a) Define Kb and explain how it is used to determine the strength of a base. [3]
b) Given that the pKa of a weak acid is 4.5, calculate the pKb of its conjugate base. [2]
Question 8
a) Describe the mechanism of buffer action in maintaining the pH of a solution. [3]
b) Why is it important to choose a weak acid or base and its salt when preparing a buffer solution? [2]
Question 9
a) Explain the difference between a strong acid and a weak acid in terms of their ionisation in water. [3]
b) If a strong acid has a pH of 2, what would be the concentration of [H+] ions in the solution? [2]
c) How does the pH of a weak acid compare to its pKa value? [2]
Question 10
a) Describe the significance of pKa in the context of acid-base equilibria. [3]
b) If a weak base, BOH, has a pKb of 5.2, calculate its Kb value. [2]
c) How would the addition of its conjugate acid, BH+, affect the pH of the BOH solution? [3]
Question 11
Which of the following solutions can act as a buffer?
A. A solution of a strong acid and its conjugate base.
B. A solution of a weak acid and its conjugate base.
C. A solution of a strong acid and a strong base.
D. A solution of water and a strong acid.
Question 12
If the degree of ionisation of a weak acid is very low, what can be said about its Ka value?
A. It will be very high.
B. It will be moderately high.
C. It will be close to zero.
D. It will be very low.
Question 13
Which of the following is NOT a common application of buffers?
A. Maintaining the pH of swimming pools.
B. In fermentation processes.
C. In car batteries.
D. In the human bloodstream.
Question 14
What is the significance of pKb in the context of bases?
A. It indicates the pH of the base.
B. It represents the concentration of the base.
C. It is the base dissociation constant, indicating the strength of a base.
D. It represents the pOH of the base solution.
Question 15
A solution has a pKa of 4.8. Which of the following is true about its acidic strength?
A. It is a very strong acid.
B. It is a moderately strong acid.
C. It is a weak acid.
D. It is a very weak acid.
Question 16
a) What is meant by the degree of ionisation of an acid? [2]
b) How is the degree of ionisation related to the strength of an acid? [2]
c) A certain weak acid has a degree of ionisation of 0.02. If 0.1 M of this acid is dissolved in water, calculate the concentration of H+ ions in the solution. [3]
Question 17
a) Define a buffer solution and explain its importance in biological systems. [3]
b) How does a buffer solution resist changes in pH when small amounts of acid or base are added? [3]
c) Given a buffer solution made from a weak acid, HA, and its salt, A-, how would the pH of the buffer change if some strong acid is added? [2]
Question 18
a) Define Ka and explain its significance in determining the strength of an acid. [3]
b) A weak acid, HA, has a Ka value of 1.8 x 10^-5. Calculate the pH of a 0.1 M solution of this acid. [3]
c) How is the value of Kb for the conjugate base, A-, related to the Ka of HA? [2]
d) If the pH of the solution in part b) is adjusted to 7 by adding a strong base, what is the ratio of the concentration of A- to HA? [3]
Question 19
a) What is meant by the term "degree of ionisation" of a weak base? [2]
b) A 0.2 M solution of a weak base, BOH, has a pH of 9. Calculate the concentration of OH- ions in this solution. [3]
c) How is the pKb of a base related to its degree of ionisation? [3]
d) Describe the mechanism of buffer action when a small amount of strong acid is added to a buffer solution consisting of BOH and its salt, B+. [4]
Question 20
a) What is the significance of pKb in the context of acid-base equilibria? [3]
b) A weak acid, HA, has a pKa of 4.8. What is the pH of a buffer solution prepared by mixing equal concentrations of HA and its salt, A-? [3]
c) How would the pH of the buffer solution in part b) change if some strong base is added? [3]
d) Describe the preparation and one application of a buffer solution in a laboratory setting. [4]