Chemical Equilibrium

Question 1

When is a chemical reaction in equilibrium?

Answer 1

When the composition of the reactants and products remains constant indefinitely.

Question 2

What does the value of equilibrium constant indicate?

Answer 2

The position of equilibrium.

Question 3

What influences the numerical value of the equilibrium constant?

Answer 3

Reaction temperature, it is independent of concentration and/or pressure.

Question 4

Influence on K for endothermic reactions

Answer 4

A rise in temperature causes an increase in K and the yield of the product is increased.

Question 5

Influence on K for exothermic reactions

Answer 5

A rise in temperature causes a decrease in K and the yield of the product is decreased.

Question 6

Does the presence of a catalyst affect the value of K

Answer 6

No

Question 7

Amphoteric

Answer 7

Can react as an acid and a base

Question 8

What is the value of the ionic product at 25 degrees Celsius?

Answer 8

1x10^-14

Question 9

What are the concentrations of H30+ and OH^- at 25 degrees

Answer 9

10^-7 mol l^-1

Question 10

Brønsted-Lowry definitions of acids and bases

Answer 10

State that an acid is a proton donor and a base is a proton acceptor.

Question 11

Strong acids

Answer 11

Completely dissociated into ions in aqueous solution. Include: Hydorchloric acid, sulphuric acid, nitric acid.

Question 12

Weak acids

Answer 12

Anything other than the three strong acids. Only dissociate partially into ions in aqueous solution. Sulfurous acid is a weak acid.

Question 13

Strong bases

Answer 13

Solutions of metal hydroxides.

Question 14

Weak bases

Answer 14

Ammonia and amines.

Question 15

Buffer solution

Answer 15

One in which the pH remains approximately constant when small amounts of acid, base or water are added.

Question 16

Acid buffer

Answer 16

Consists of a solution of a weak acid and one of its salts made from a strong base.

Question 17

How does an acid buffer regulate pH?

Answer 17

The weak acid provides hydrogen ions when these are removed by the addition of small addition of a small amount of base. The salt of the weak acid provides the conjugate base, which can absorb excess hydrogen ions produced by the addition of a small amount of acid.

Question 18

Basic buffer

Answer 18

Consists of a solution of a weak base and one of its salts.

Question 19

How does a basic buffer regulate pH?

Answer 19

The weak base removes excess hydrogen ions, and the conjugate acid provided by the salt supplies hydrogen ions when these are removed.

Question 20

Indicators

Answer 20

Weak acids. In aqueous solution the colour of an acid indicator is distinctly different from that of its conjugate base.