Changing the surface area of the reactants
3 marks · EasyThe graph below shows how the mass of carbon dioxide produced changes over time during the reaction between excess hydrochloric acid and two forms of calcium carbonate, both of the same mass.
Which form of calcium carbonate reacts faster? Give evidence from the graph.
State the total mass of carbon dioxide produced at the end of both reactions.
Explain why both forms produce the same final mass of carbon dioxide.
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.
Show answer
(a) Powder; it reaches maximum CO2 much faster (steeper curve).
(b) 1.6 g
(c) Same mass of reactants used in both reactions, so same amount of CO2 produced.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Identifies powder as faster, with correct evidence from the graph (steeper rise/reaches maximum faster).
A1 (b) · 1 mark · Reads the final mass correctly from the graph (1.6 g).
M1 (c) · 1 mark · States that equal/reactant masses give equal CO2 produced, or explains correctly.
Worked solution
a) Powder reacts faster because the powder's curve rises more steeply and reaches 1.6 g before the lumps do.
b) Both reactions produce 1.6 g of CO2.
c) Because the same amount of reactant is used in both, they produce the same amount of CO2.