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IB DP Chemistry Questions

8.1 Theories of Acids and Bases

Question 1

Which of the following best describes an acid according to the Brønsted-Lowry theory?

A. A substance that donates a proton.

B. A substance that accepts a proton.

C. A substance that donates an electron.

D. A substance that accepts an electron.

Question 2

What is the conjugate base of H2O when it acts as an acid?

A. OH-

B. H3O+

C. H2O

D. H+

Question 3

Which of the following is NOT a limitation of the Arrhenius theory of acids and bases?

A. It only applies to aqueous solutions.

B. It does not explain the acidic behaviour of substances like NH3.

C. It defines acids as proton donors.

D. It is based on the formation of ions.

Question 4

In the reaction: NH3 + H2O -> NH4+ + OH-, which species is the acid?

A. NH3

B. H2O

C. NH4+

D. OH-

Question 5

Which of the following pairs represents a conjugate acid-base pair?

A. H2O and H3O+

B. H2O and OH-

C. H+ and OH-

D. H2O and H2O

Question 6

a) Define an acid and a base according to the Brønsted-Lowry theory. [2]

b) Given the reaction: NH3 + H2O -> NH4+ + OH-, identify the conjugate acid-base pairs. [2]

Question 7

a) Describe the limitations of the Arrhenius theory of acids and bases. [3]

b) How does the Brønsted-Lowry theory overcome these limitations? [2]

Question 8

a) Given the equation: HCl + H2O -> H3O+ + Cl-, explain the acid-base behaviour in terms of proton transfer. [2]

b) If the concentration of H3O+ ions in the solution is 0.01 M, calculate the pH of the solution. [2]

Question 9

a) Describe the difference between a strong acid and a weak acid in terms of their degree of ionisation. [3]

b) Given that acetic acid (CH3COOH) is a weak acid, explain its behaviour when dissolved in water. [2]

c) Why is the pH of a 0.1 M solution of hydrochloric acid (HCl) lower than that of a 0.1 M solution of acetic acid? [2]

Question 10

a) Define a conjugate acid-base pair and provide an example. [2]

b) If the concentration of OH- ions in a solution is 0.001 M, calculate the pOH of the solution. [2]

c) How can you determine the pH of the solution using the pOH value? [2]

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