Neutralise an acid

Question 1

What is neutralisation?

Answer 1

Reaction between an acid and a base

Question 2

What is a base?

Answer 2

Any substance that reacts with an acid to form a salt and water only. This means that metal oxides and metal hydroxides are bases

Question 3

What are bases called that are soluble in water?

Answer 3

Alkali and they dissolve in water to form alkaline solutions. For example:

• copper oxide is a base, but it is not an alkali because it is insoluble in water
• sodium hydroxide is a base, and it dissolves in water so it is also an alkali

Question 4

What happens in an acid-alkali reaction?

Answer 4

Hydrogen ions from the acid react with hydroxide ions from the alkali.

Question 5

When is a solution neutral?

Answer 5

if the concentration of hydrogen ions is the same as the concentration of hydroxide ions
Neutral solution: [H+] = [OH-]
where [H+] = concentration of hydrogen ions in solution
and [OH-] is the concentration of hydroxide ions in solution

Question 6

How do you carry out a neutralisation reaction?

Answer 6

1) Use the measuring cylinder to add 50 cm3 of dilute hydrochloric acid to the beaker.
2) Estimate and record the pH of the contents of the beaker:
- Put a piece of universal indicator paper onto the white tile.
- Dip the end of the glass rod into the liquid, then tap it onto the universal indicator paper.
- Wait 30 seconds, then match the colour to the appropriate pH on the pH colour chart.
- Rinse the glass rod with water.
3) Measure out 0.3 g of calcium hydroxide powder onto a piece of paper or a ‘weighing boat’.
4) Add the calcium hydroxide powder to the beaker, stir, then estimate and record the pH of the mixture.
5) Repeat step 4 seven times so that you add a total of 2.4 g of calcium hydroxide powder to the acid.