CC8 Acids

Question 1

What does soluble mean? What does insoluble mean?

Answer 1

Dissolves in water. Does not dissolve in water

Question 2

Define acid in terms of pH

Answer 2

A substance with a pH of less than 7

Question 3

Define acids in terms of ions

Answer 3

A substance which releases H⁺ ions in solution

Question 4

State the three common acids and give their formulae

Answer 4

Hydrochloric acid, HCl(aq), Sulphuric acid, H₂SO₄(aq), Nitric acid, HNO₃

Question 5

Define pH in terms of ions

Answer 5

Below pH 7 the lower the pH the higher the concentration of H+ ions. Above pH 7 the higher the pH the higher the concentration of OH- ions

Question 6

What is a neutral solution?

Answer 6

A solution with a pH of 7. It has the same concentration of H+ and OH- ions. Water is an example.

Question 7

How do you measure pH?

Answer 7

With an indicator or pH probe/ pH meter

Question 8

What is a base?

Answer 8

A substance that will neutralise an acid. E.g. copper oxide

(metal oxides, hydroxides and carbonates)

Question 9

What is an alkali?

Answer 9

A soluble base. E.g. sodium hydroxide

Question 10

Which ions are always present in a solution of an alkali?

Answer 10

OH⁻

Question 11

What is a strong acid?

Answer 11

An acid which completely splits up into its ions in water. E.g. when HCl is in water all the HCl molecules split up into H⁺ and Cl⁻.

Question 12

What is a weak acid?

Answer 12

An acid which will have some molecules which do not split up into their ions. E.g. in ethanoic acid only some of the molecules will have split up into the ethanoate ion and H⁺ ions.

Question 13

What is the relationship between an acid of pH2 and an acid of pH 3?

Answer 13

pH 2 is 10 times more hydrogen ions than pH 3

Question 14

What is a concentrated acid?

Answer 14

An acid where there are lots of acid particles in the water.

Question 15

What is a dilute acid?

Answer 15

An acid where there are fewer acid particles in the water.

Question 16

What colour is litmus in acid and alkali?

Answer 16

Acid – red, alkali – blue

Question 17

What colour is methyl orange in acid and alkali?

Answer 17

Acid – red, alkali – yellow

Question 18

What colour is phenol phthalein in acid and alkali?

Answer 18

Acid – colourless, alkali – pink

Question 19

What colour is copper sulphate solution?

Answer 19

blue

Question 20

What salt makes a blue solution?

Answer 20

Copper sulfate