Chemistry · Oct / Nov 2025 · Paper 11 · Question 15

The rate of reaction between calcium carbonate and dilute hydrochloric acid is measured in three separate experiments. [diagram of conical flask with cotton wool, dilute hydrochloric acid, 2 g calcium carbonate, on a mass balance] In experiment 1, the calcium carbonate is powdered, and an excess of hydrochloric acid is used. In experiment 2, the calcium carbonate is in lumps, and an excess of hydrochloric acid is used. In experiment 3, the calcium carbonate is in lumps, less hydrochloric acid is used, and the calcium carbonate is in excess. The results of these experiments are shown. [graph of mass balance reading against time with curves X, Y and Z] Which statement is correct?

1. AExperiment 1 is shown by curve X.
2. BExperiment 1 is shown by curve Y.
3. CExperiment 2 is shown by curve Y.
4. DExperiment 3 is shown by curve Z.

As printed in the paper