Chemistry · May / June 2016 · Paper 11 · Question 19

The diagram shows the apparatus used to measure the rate of the reaction between calcium carbonate and dilute hydrochloric acid. The mass of the flask and the contents is measured at regular intervals of time. [diagram: conical flask containing dilute hydrochloric acid and calcium carbonate, with cotton wool at the top, on a balance] Which graph correctly shows how the mass of the flask and contents changes with time?

1. Agraph: mass decreasing rapidly then levelling off (exponential decay)
2. Bgraph: mass decreasing linearly to zero
3. Cgraph: mass decreasing rapidly then levelling off at a non-zero value
4. Dgraph: mass decreasing slowly then rapidly to zero

As printed in the paper