Experiments to measure the rate of reaction
4 marks · NormalDraw a labelled diagram of the apparatus you could use to measure the loss of mass during the reaction between excess marble chips and dilute hydrochloric acid.
Explain why cotton wool is placed in the neck of the flask during this experiment.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Diagram shows: conical flask with marble chips and dilute hydrochloric acid, cotton wool in neck, setup on balance. Labels indicate all key parts. · must show a balance shown under flask, flask with 'marble chips' and 'dilute HCl', cotton wool in neck
(b) The cotton wool allows carbon dioxide gas to escape but prevents acid from splashing out. · must show allows gas to escape, prevents acid spitting
Must show: conical flask, balance, marble chips, dilute acid, cotton wool shown in neck
Common mistakes: drawing sealed flask; not showing balance
Show mark scheme and worked solution
Marking points
D1 (a) · 2 marks · Correct labelled diagram with a conical flask containing marble chips and dilute hydrochloric acid on a balance, with cotton wool in the neck.
M1 (b) · 1 mark · States cotton wool allows CO2 gas to escape.
M2 (b) · 1 mark · States cotton wool prevents acid spitting out.
Worked solution
Cotton wool is placed in the neck to allow carbon dioxide to escape but to stop any acid from spitting out.