(i) Any one of:

different units / solubility expressed in different ways «mass of gas in some sources, volume of gas in others; per volume of water in some, per mass of water in another» ✔

OR

the pressure of the chlorine gas is not stated ✔

OR

different precisions / numbers of significant figures ✔

OR

uncertainties of the values are not given ✔

OR

the density of the gas «needed for sources B and E» is not given ✔

(ii) «mass of chlorine =» 0.152 «$\mathrm{dm^3}$» × 2.80 «$\mathrm{g\,dm^{-3}}$» = 0.426 «g» ✔

«solubility =» 0.426 «g» / 70.90 «$\mathrm{g\,mol^{-1}}$» / 0.100 «$\mathrm{dm^3}$» = 0.0600 «$\mathrm{mol\,dm^{-3}}$

OR

«$n = \frac{PV}{RT} = \frac{101\,300 \times 1.52 \times 10^{-4}}{8.31 \times 308}$

0.0602 «$\mathrm{mol\,dm^{-3}}$» ✔

(iii) «solubility decreases as the temperature rises, so» dissolving chlorine in water is exothermic «and the equilibrium shifts towards undissolved gas at higher temperature» ✔

OR

«at higher temperature» the molecules have more kinetic energy and can break free of the attractions holding chlorine molecules among water molecules «so more gas escapes from the solution» ✔

OR

the negative entropy change of dissolving a gas becomes more significant «−TΔS more positive» at higher temperature ✔

(i) [1 max] for any one valid difficulty. (ii) M1: mass of chlorine from the volume of gas and its density (0.426 g); M2: division by M(Cl2) = 70.90 g mol−1 and by 0.100 dm3 to give 0.0600 mol dm−3. Award [2] for a correct final answer with working; accept 0.0594-0.0602 from PV = nRT (0.0594 with P = 100 kPa, 0.0602 with P = 101.3 kPa). ECF from M1. (iii) [1] for any explanation consistent with a decrease in solubility as temperature increases.