This question is about acids and alkalis - AQA - GCSE Chemistry - Question 2 - 2019 - Paper 1

The word equation for the reaction between calcium hydroxide and an acid to form calcium chloride is:

calcium hydroxide + hydrochloric acid → calcium chloride + water.

Apparatus A is identified as a burette.

The reading on apparatus A is 27.6 cm³.

To determine which sample, P or Q, is more concentrated, the student should follow these steps:

1. Measure the volume of dilute sulfuric acid (25.0 cm³) using a pipette and transfer it into a conical flask.
2. Add a few drops of a suitable indicator to the flask to visualize the endpoint of the titration.
3. Fill the burette with the sodium hydroxide solution.
4. Slowly add sodium hydroxide to the acid while swirling the flask until the solution changes color, indicating the endpoint is reached.
5. Record the volume of sodium hydroxide used.
6. Repeat the titration with the other sample of acid (either P or Q) and note the volume of sodium hydroxide used for neutralization.
7. Compare the volumes; the sample requiring a higher volume of sodium hydroxide is more concentrated.