When \({\text{100 c}}{{\text{m}}^{\text{3}}}\) of \({\text{1.0 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) HCl is mixed with \({\text{100 c}}{{\text{m}}^{\text{3}}}\) of \({\text{1.0 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) NaOH, the temperature of the resulting solution increases by 5.0 °C. What will be the temperature change, in °C, when \({\text{50 c}}{{\text{m}}^{\text{3}}}\) of these two solutions are mixed?

A.     2.5

B.     5.0

C.     10

D.     20

B

There were three G2 comments on this question. Some suggested that it would be better if more consistent use of significant figures would be used, which is noted and one stated that the question was complicated. The question was certainly challenging for candidates and only 36.27% of candidates got the correct answer B.