JAMB Chemistry 2012 Paper

Concept:Rate of $\mathrm{CO}_2$ production increases with higher acid concentration and larger surface area of $\mathrm{CaCO}_3$ powder.Explanation:Powdered $\mathrm{CaCO}_3$ has a larger surface area than lumps, so it reacts faster.A higher concentration of HCl also increases the rate of reaction.Comparing options, the highest concentration is $0.10\ \mathrm{mol\ dm^{-3}}$ HCl, and it is combined with powdered $\mathrm{CaCO}_3$.Therefore, option C gives the fastest production of carbon(IV) oxide.Answer:C. $0.10\ \mathrm{mol\ dm^{-3}}$ HCl and $5\mathrm{g}$ powdered $\mathrm{CaCO}_3$