Chapter 11

Question 1

What is an acid?

Answer 1

A substance producing hydrogen ions, H+, in aqueous solution.

Question 2

What is a base?

Answer 2

Any metal oxide or hydroxide that reacts with an acid to produce a salt and water only.

Question 3

What is an alkali?

Answer 3

A substance producing hydroxide ions, OH-, in aqueous solution.

Question 4

What happens in a neutralisation reaction?

Answer 4

The hydrogen ions, H+, from the acid and the hydroxide ions, OH-, from the alkali react to form water.
H+ (aq) + OH- (aq) -> H2O (l)

Question 5

What is a strong acid?

Answer 5

An acid that is completely ionised in aqueous solution.

Question 6

What is a weak acid?

Answer 6

An acid that is only partially ionised in aqueous solution.

Question 7

What are the colour changes of methyl orange, screened methyl orange, litmus, bromothymol blue and phenolphthalein indicators? What pH range do the colour change occur?

Answer 7

• Methyl orange: red to yellow (3-5)
• Screened methyl orange: violet to green (3-5)
• Litmus: red to blue (5-8)
• Bromothymol blue: yellow to blue (6-8)
• Phenolphthalein: colourless to pink (8-10)