Core practical - investigating neutralisation

Question 1

Aims of this experiment:

Answer 1

To investigate the change in pH when adding powdered calcium hydroxide to a fixed volume of dilute hydrochloric acid.

Question 2

apparatus needed: (5)

Answer 2

• measuring cylinder
• beaker
• glass rod
• universal indicator paper
• spatula

Question 3

Method: (5)

Answer 3

1- Use a measuring cylinder to add dilute hydrochloric acid to a beaker.
2- Dip a clean glass rod into the contents of the beaker. Use it to transfer a drop of liquid to a piece of universal indicator paper on a white tile. Wait 30 seconds, then match the colour to a pH colour chart. Record the estimated pH.
3- Add a level spatula of calcium hydroxide powder to the beaker.
4- Stir thoroughly, then estimate and record the pH of the mixture (as in step 2).
5- Repeat steps 3 and 4 until there are no more changes in pH.

Question 4

how should the graph be plotted? (2)

Answer 4

• pH on the vertical axis

- number of spatulas added on the horizontal axis

Question 5

Suggest two ways in which more accurate results could be obtained. (2)

Answer 5

• You could measure the mass of calcium hydroxide powder using a balance.
• You could also use a pH probe and meter to measure the pH, rather than estimating it using universal indicator.

Question 6

what are the hazard in this practical? (2)

Answer 6

Hydrochloric acid and Calcium hydroxide powder

Question 7

possible harm from and precautions for: Hydrochloric acid (2)

Answer 7

harm: Concentrated acid is corrosive and damages skin and clothes
precaution: Use dilute hydrochloric acid

Question 8

possible harm from and precautions for: Calcium hydroxide powder (4)

Answer 8

harm: Causes serious eye damage, May cause respiratory irritation
precaution: Wear eye protection, Avoid making a dust