CIE iGCSE Co-Ordinated Science C6.2 Rate of reaction Exam Style Questions Paper 4
Question
A student investigates the reaction between calcium carbonate and dilute hydrochloric acid.
The student does the experiment using three different sets of conditions, A, B and C.
All other variables are kept the same.
Fig. 8.1 shows the three sets of conditions.
(a) State which set of conditions, A, B or C, will give the fastest rate of reaction.
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(b) The equation for the reaction in the student’s experiment is shown.
CaCO$_{3}$+ 2HCl → CaCl$_{2}$ + H$_{2}$O + CO$_{2}$
Calculate the mass of 1.2dm$^{3}$ of carbon dioxide gas measured at room temperature and pressure (r.t.p.).
The volume of one mole of any gas is 24dm$^{3}$ at r.t.p.
Show your working.
[A$_{r}$: C, 12; O, 16]
mass of carbon dioxide gas = ……………………………………………….g
(c) The reaction between calcium carbonate and dilute hydrochloric acid is exothermic.
State what is meant by an exothermic reaction.
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(d) A food company is making new self-heating cans of soup.
They investigate three different reactions.
Fig. 8.2 shows the reaction profiles for the three reactions, X, Y and Z.
The reaction profiles show:
• the energy change in the reaction
• the activation energy of the reaction.
(i) State what is meant by activation energy.
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(ii) Suggest which reaction, X, Y or Z, would be most suitable to use in the self-heating cans.
Explain your answer.
reaction ………………………………….
explanation …………………………………………………………………………………………………………
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▶️Answer/Explanation
Ans : 8(a) C ;
8(b) (Mr of CO$_{2}$ =) 44 ;
(moles of CO$_{2}$ = 1.2 ÷ 24 =) 0.05 ;
(mass of CO$_{2}$ = 0.05× 44 =) 2.2 (g) ;
8(c) (reaction in which) energy is given out / heat is given out ;
8(d)(i) minimum amount of energy ;
required for reaction to take place ;
8(d)(ii) (reaction) X ;
(because) Z is endothermic / Z does not give out heat (energy) ;
(because) X has a lower activation energy than Y / X gives out more energy / heat than Y ;