7.102 g of \({\text{N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4}{\text{ (}}M = 142.04{\text{ g}}\,{\text{mo}}{{\text{l}}^{ - 1}}{\text{)}}\) is dissolved in water to prepare \({\text{0.5000 d}}{{\text{m}}^{\text{3}}}\) of solution. What is the concentration of \({\text{N}}{{\text{a}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}\) in \({\text{mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\)?

A.     \(2.500 \times {10^{ - 2}}\)

B.     \(1.000 \times {10^{ - 1}}\)

C.     \(1.000 \times 10\)

D.     \(1.000 \times {10^2}\)

B

There was some concern that, for the mathematically challenged, the figures given were too difficult. Although it could perhaps have been simplified to 7.1 g and \({\text{142 g}}\,{\text{mo}}{{\text{l}}^{ - 1}}\) nearly 57% of candidates gave the correct answer, the next most common being A (nearly 25%) which showed an incorrect concentration calculation.