CAPE Chemistry Unit 2 · 2015 · Paper 1 · Question Q19

Items 19-20 refer to the following information. A student carries out the gravimetric analysis of a soil sample taken from an area surrounding a garage. The soil sample is found to be contaminated with \text{Pb}^{2+} ions. 100\text{ cm}^3 of a solution obtained from the sample when mixed with 25\text{ cm}^3 of 0.100\text{ mol dm}^{-3}\text{ HCl} yields 0.010\text{ g} of lead chloride. [The relative formula mass of lead chloride is 278.2.] The balanced equation for the reaction between lead ions and hydrochloric acid is

1. (A)\text{Pb(s)} + 2\text{HCl(aq)} \rightarrow \text{PbCl}_2(\text{s}) + \text{H}_2(\text{g})
2. (B)2\text{Pb(s)} + 2\text{HCl(aq)} \rightarrow 2\text{PbCl(s)} + \text{H}_2(\text{g})
3. (C)\text{Pb}^{2+}(\text{aq}) + 2\text{HCl(aq)} \rightarrow \text{PbCl}_2(\text{aq}) + 2\text{H}^+(\text{aq})
4. (D)\text{Pb}^{2+}(\text{aq}) + 2\text{HCl(aq)} \rightarrow \text{PbCl}_2(\text{s}) + 2\text{H}^+(\text{aq})