Acids and Bases

Question 1

What are Brønsted–Lowry acids?

Answer 1

proton donors

Question 2

What are Brønsted–Lowry bases?

Answer 2

proton acceptors

Question 3

What are strong acids?

Question 4

What are strong bases?

Answer 4

Bases that completely ionise in water.

Question 5

What are weak acids?

Question 6

What is the ionic product of water?

Question 7

Why do we consider the concentration of the water a constant?

Answer 7

There is so much water compared to hydrogen and hydroxide ions that the water can be considered to have a constant concentration.

Question 8

What equation do you use to find the hydrogen concentration of pure water?

Answer 8

1.00 × 10–14

Question 9

What are the equations that link pH and hydrogen ion concentration?

Question 10

Calculate the pH of 0.10 mol dm–3 hydrochloric acid.

Question 11

Calculate the pH of 0.100 mol dm–3 sulfuric acid.

Question 12

The value of Kw at 298 K is 1.0 × 10–14 mol2 dm–6. Find the pH of 0.100 mol dm–3 NaOH at 298 K

Question 13

What is the acid dissociation constant?

Question 14

Find the pH of a 0.020 mol dm–3 solution of propanoic acid (CH3CH2COOH) at 298K. Ka
for propanoic acid at this temperature is 1.30 × 10–5 mol dm–3

Question 15

How do you find pKa?

Question 16

How do you find Ka using pKa?

Question 17

How do you find pH using Ka?

Answer 17

pH = pKa

Question 18

How to identify which indicator to use?

Answer 18

The pH range must lie entirely on the vertical point of the titration curve.

Question 19

What is a buffer?

Answer 19

A solution that resists changes in pH when a small amount of acid or alkali is added.

Question 20

What are acidic buffers made out of?

Answer 20

1. A weak acid and a strong base.
2. A weak acid and one of its salts.

Question 21

What effect does adding an acid have on an acidic buffer?

Answer 21

1. The H+ concentration increases.
2. The excess H+ ions combine with the A- ions and the equilibrium shifts to the left.
3. This causes the H+ concentration to decrease.

Question 22

What effect does adding an alkali have on an acidic buffer?

Answer 22

1. The OH- concentration increases and H+ decreases.
2. The excess OH- ions react with the H+ ions to form water.
3. The equilibrium shifts to the right so that the acid dissociates to release more H+ ions.

Question 23

What are basic buffers made out of?

Answer 23

A weak base and one of its salts.

Question 24

What effect does adding an acid have on an acidic buffer?

Answer 24

1. The H+ concentration increases and OH- decreases.
2. The excess H+ ions react with the OH- ions to form water.
3. The equilibrium shifts to the right so more of the base dissociates to release OH- ions.

Question 25

What effect does adding an alkali have on an acidic buffer?

Answer 25

1. The H+ concentration decreases and the OH- concentration increases.
2. The excess OH- ions will react with the positive ion to make H2O and the equilibrium shifts to the left to remove the OH- ions.