20 Acids, Bases and pH

Question 1

Bronsted-Lowry acid

Answer 1

Proton donor.

Question 2

Bronsted-Lowry base

Answer 2

Proton acceptor.

Question 3

What is a conjugate-base pair?

Answer 3

A conjugate-base pair contains two species that can be interconverted by transfer of a proton. They differ by H+.

Question 4

What are mono/di/tribasic acids?

Answer 4

These refer to the total number of hydrogen ions that can be replaced in acid-base reactions e.g. by a metal ion, to form a salt.

Question 5

Acid + carbonate forms…

Answer 5

Salt + water + carbon dioxide

Question 6

Acid + metal forms…

Answer 6

Salt + hydrogen

Question 7

Acid + metal oxide OR metal hydroxide OR alkali forms…

Answer 7

Salt + water

Question 8

What is a strong acid?

Answer 8

An acid that completely dissociates in solution.

Question 9

What is a weak acid?

Answer 9

An acid that partially dissociates in solution.

Question 10

What does a larger acid dissociation constant suggest?

Answer 10

The greater the dissociation of the acid, therefore the greater the acid strength.

Question 11

Approximations for weak acid calculations

Answer 11

[H+] equilibrium ~ [A–] equilibrium i.e. negligible dissociation of water.

[HA] equilibrium ~ [HA] undissociated i.e. [HA]&raquo_space; [H+]

Question 12

Limitations of approximations for weak acid calculations

Answer 12

• Assumes dissociation of water is negligible but this breaks down for very weak acids.
• Assumes concentration of acid is much greater than concentration of hydrogen ions at equilibrium, but this breaks down for stronger weak acids.