The progress of the reaction was followed by measuring the volume of gas produced at particular time intervals. The results are shown.

$\backslash$table$[[$Time $/$ s$,0,10,20,30,40,50,60,70,80,100,120],[$Volume of gas $\frac{?}{c{m}^3},0,9,16,22,27\mathrm{.}5,32,36,39\mathrm{.}5,42,45,45]]$

a Plot a suitable graph of these results. Label the axes.

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b Calculate the initial rate of reaction by drawing a tangent. Show how you worked out

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your answer on the graph. Include the correct units.

c Describe how the rate of reaction changes with time and explain how you know this by

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referring to the line of the graph.

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d Describe how to calculate the rate of reaction at $40s.$

e The mass of calcium carbonate used was $0\mathrm{.}1875g.$ The volume of $0\mathrm{.}100mold{m}^{-3}$ hydrochloric acid used was $40c{m}^3.M_{r}CaC{O}_3=100\mathrm{.}1$

Demonstrate by calculation that the calcium carbonate was the limiting reagent.

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f The concentration of hydrochloric acid was doubled. On your graph draw a line to show how the rate of reaction changes with time.

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$[$Total: $16]$

$2$ a Explain why gases react together faster at higher pressure.

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