Acids, bases and buffers

Question 1

What is a Bronstead-Lowry acid?

Answer 1

A substance that can donate a proton.

Question 2

What is a Bronstead-Lowry base?

Answer 2

A substance that can accept a proton.

Question 3

Can H2O act as an acid or a base?

Answer 3

Both

Question 4

What is the equilibrium expression for H2O?

Answer 4

Kc= [H][OH] / [H2O]

Question 5

What is the ionic product of water?

Answer 5

Kw

Question 6

What is the expression of Kw?

Answer 6

Kw = [H] [OH]

Question 7

What is the expression for pH?

Answer 7

pH = -log [H]

Question 8

Why does the value of Kw increase as the temperature increases?

Answer 8

Dissociation of water is endothermic. Increasing the temperature favours this direction so increases the value of Kw.

Question 9

Why is water not acidic at a higher temperature?

Answer 9

Same concentrations of H and OH

Question 10

Is an acid that fully dissociates strong or weak?

Answer 10

Strong

Question 11

Is a base that partly dissociated strong or weak?

Answer 11

Weak

Question 12

Do acids get stronger or weaker as the acid dissociation constant increases?

Answer 12

Stronger, the equilibrium is further right.

Question 13

Write an expression for Ka.

Answer 13

Ka = [H] [A] / [HA]

Question 14

Write an expression for Ka if the acid is weak and in aqueous solution.

Answer 14

Ka = [H]^2 / [HA]

Question 15

What is the equivalence point?

Answer 15

The point at which sufficient base has been added to just neutralise the acid.

Question 16

Is HCl a strong or weak acid?

Answer 16

Strong

Question 17

Is NaOH a strong or weak base?

Answer 17

Strong

Question 18

Is Ethanoic acid (CH3COOH) a strong or weak acid?

Answer 18

Weak

Question 19

Is NH3 a strong or weak base?

Answer 19

Weak

Question 20

How does the half-neutralisation point allow you to find the pKa of a weak acid?

Answer 20

ka = [H]
-log(Ka) = -log[H]
pKa = pH

Question 21

What is an acidic buffer made from?

Answer 21

A mixture of a weak acid and a soluble salt of that acid.