Acids, Bases, Strong And Weak Acids

Question 1

What is an acid?

Answer 1

A substance that releases H⁺ ions in aqueous solution.

Question 2

What is a base?

Answer 2

A substance that can neutralise an acid by accepting H⁺ ions.

Question 3

What is an alkali?

Answer 3

A soluble base that releases OH⁻ ions in solution.

Question 4

What is the pH scale used for?

Answer 4

To measure how acidic or alkaline a solution is.

Question 5

What pH values indicate an acid?

Answer 5

pH less than 7.

Question 6

What pH values indicate an alkali?

Answer 6

pH greater than 7.

Question 7

What pH value is neutral?

Answer 7

pH 7.

Question 8

What happens to pH as H⁺ ion concentration increases?

Answer 8

pH decreases (becomes more acidic).

Question 9

What is a neutralisation reaction?

Answer 9

An acid reacts with a base to form a salt and water.

Question 10

What is the general equation for acid + base?

Answer 10

Acid + Base → Salt + Water.

Question 11

What is the general equation for acid + metal carbonate?

Answer 11

Acid + Metal Carbonate → Salt + Water + Carbon Dioxide.

Question 12

What is the general equation for acid + metal?

Answer 12

Acid + Metal → Salt + Hydrogen.

Question 13

What is the difference between strong and weak acids?

Answer 13

Strong acids fully ionise in water; weak acids only partially ionise.

Question 14

What is ionisation?

Answer 14

The process of a molecule splitting into ions in solution.

Question 15

Give an example of a strong acid.

Answer 15

Hydrochloric acid (HCl), sulfuric acid (H₂SO₄), nitric acid (HNO₃).

Question 16

Give an example of a weak acid.

Answer 16

Ethanoic acid (CH₃COOH), citric acid, carbonic acid.

Question 17

What happens to the pH of a strong acid compared to a weak acid of the same concentration?

Answer 17

The strong acid has a lower pH (more acidic).

Question 18

Does concentration affect acid strength?

Answer 18

No, strength is about ionisation; concentration is about how much acid is dissolved.

Question 19

What is a salt?

Answer 19

A compound formed when the hydrogen in an acid is replaced by a metal or ammonium ion.

Question 20

What ions do acids release in water?

Answer 20

H⁺ ions.

Question 21

What ions do alkalis release in water?

Answer 21

OH⁻ ions.

Question 22

What is a titration?

Answer 22

An experiment to find the exact volume of acid needed to neutralise an alkali (or vice versa).

Question 23

What is a suitable indicator for a titration?

Answer 23

Phenolphthalein or methyl orange.

Question 24

What does phenolphthalein show in acid and alkali?

Answer 24

Colourless in acid, pink in alkali.

Question 25

What is the main purpose of titrations?

Answer 25

To calculate the concentration of an unknown acid or alkali.