Question 1
Which of the following statements is true regarding the relationship between Ka, Kb, and Kw for a conjugate acid-base pair?
A. Ka x Kb = Kw
B. Ka + Kb = Kw
C. Ka / Kb = Kw
D. Ka - Kb = Kw
Question 2
Given that the Ka for a weak acid is 1.0 x 10^-5, what is the Kb for its conjugate base if Kw = 1.0 x 10^-14?
A. 1.0 x 10^-9
B. 1.0 x 10^-5
C. 1.0 x 10^-19
D. 1.0 x 10^-10
Question 3
A strong acid is one that:
A. Has a low Ka value
B. Completely dissociates in water
C. Has a high Kb value
D. Partially dissociates in water
Question 4
Which of the following is NOT a characteristic of a weak base?
A. It has a low Kb value
B. It partially dissociates in water
C. It has a high Ka value
D. It does not release all its hydroxide ions in water
Question 5
If the Kb of ammonia (NH3) is 1.8 x 10^-5, what is the Ka of its conjugate acid (NH4+)?
A. 5.6 x 10^-10
B. 1.8 x 10^-5
C. 5.6 x 10^-20
D. 1.8 x 10^-10
Question 6
a) Define the terms Ka and Kb in the context of acid-base chemistry. [2]
b) Given that the value of Kw is 1.0 x 10^-14 at 25°C, calculate the value of Kb for an acid with a Ka of 1.8 x 10^-5. [3]
Question 7
a) Explain the relationship between the magnitude of Ka and the strength of an acid. [2]
b) A weak base B has a Kb of 2.5 x 10^-6. Predict the pH of a 0.1 M solution of this base at 25°C. [3]
Question 8
a) Describe the difference between a Lewis acid and a Brønsted-Lowry acid. [3]
b) Given a weak acid HA with a Ka of 3.2 x 10^-4, determine whether the acid is strong or weak based on its dissociation constant. [2]
Question 9
a) Describe how the strength of an acid can be predicted from its dissociation constant, Ka. [2]
b) A solution of a weak acid, HA, has a pH of 3.5. Calculate the concentration of H+ ions in the solution. [2]
c) If the concentration of HA in the solution is 0.1 M, determine its Ka value. [3]
Question 10
a) Define a Lewis base and explain how it differs from a Brønsted-Lowry base. [3]
b) Given that Kw is 1.0 x 10^-14 at 25°C, and the Ka for an acid HA is 2.0 x 10^-6, calculate the Kb for its conjugate base A-. [2]
c) Would A- be considered a strong or weak base? Justify your answer. [2]
Question 11
Which of the following acids has the strongest acidic character?
A. Ka = 1.0 x 10^-3
B. Ka = 1.0 x 10^-5
C. Ka = 1.0 x 10^-7
D. Ka = 1.0 x 10^-9
Question 12
A solution has a [OH-] concentration of 1.0 x 10^-3 mol/L. What is the [H+] concentration?
A. 1.0 x 10^-11 mol/L
B. 1.0 x 10^-3 mol/L
C. 1.0 x 10^-7 mol/L
D. 1.0 x 10^-14 mol/L
Question 13
Which of the following is true about a solution with a pH of 7?
A. It is acidic
B. It is basic
C. It is neutral
D. It has a high Ka value
Question 14
A weak acid has a Ka of 1.0 x 10^-6. 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 very weak acid
D. It is a moderately weak acid
Question 15
What is the Kb of a base if its conjugate acid has a Ka of 2.5 x 10^-4?
A. 4.0 x 10^-11
B. 2.5 x 10^-4
C. 4.0 x 10^-10
D. 2.5 x 10^-10
Question 16
a) What is the significance of the equivalence point in a titration? [3]
b) In a titration of a weak acid with a strong base, describe the pH at the equivalence point. [2]
c) Explain why the pH at the equivalence point is not necessarily 7. [3]
Question 17
a) What is the relationship between Ka, Kb, and Kw? [2]
b) If a solution of a weak base B has a Kb of 4.5 x 10^-9, predict the pH of a 0.05 M solution of this base at 25°C. [3]
c) How would the pH change if the concentration of B was doubled? [2]
Question 18
a) Describe the relationship between the dissociation constants Ka and Kb for a conjugate acid-base pair. [2]
b) A weak acid, HA, has a Ka of 1.8 x 10^-5. Calculate the Kb for its conjugate base, A-. [2]
c) If a 0.1 M solution of A- has a pH of 9.2, determine the concentration of OH- ions in the solution. [3]
d) How would the concentration of OH- ions change if the temperature of the solution was increased? Justify your answer. [3]
Question 19
a) Define the term 'buffer solution'. [2]
b) Explain how a buffer solution resists 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 conjugate base, A-, with equal concentrations of 0.1 M, calculate the pH of the buffer if the Ka for HA is 2.0 x 10^-6. [4]
d) How would the pH of the buffer solution change if some strong acid was added to it? [3]
Question 20
a) Differentiate between a strong acid and a weak acid based on their dissociation in water. [2]
b) If the pOH of a 0.05 M solution of a strong base is 2.3, determine the concentration of H+ ions in the solution. [3]
c) Using the above information, calculate the pH of the solution. [2]
d) Describe how the pH would change if the concentration of the strong base was halved. [3]