A gas with a molar mass (\(M\)) of \({\text{44 g}}\,{\text{mo}}{{\text{l}}^{ - 1}}\) occupies a volume of \(2.00 \times {10^3}{\text{ c}}{{\text{m}}^3}\) at a pressure of \(1.01 \times {10^5}{\text{ Pa}}\) and a temperature of 25 °C. Which expression is correct for the calculation of the mass of the gas, in g? \((R = 8.31{\text{ J}}\,{{\text{K}}^{ - 1}}\,{\text{mo}}{{\text{l}}^{ - 1}})\)

A.     \(\frac{{44 \times 1.01 \times {{10}^5} \times 2.00 \times {{10}^{ - 3}}}}{{8{\text{.}}31 \times 298}}\)

B.     \(\frac{{44 \times 1{\text{.}}01 \times {{10}^5} \times 2.00 \times {{10}^3}}}{{8{\text{.}}31 \times 25}}\)

C.     \(\frac{{1{\text{.}}01 \times {{10}^5} \times 2.00 \times {{10}^{ - 3}}}}{{44 \times 8{\text{.}}31 \times 298}}\)

D.     \(\frac{{44 \times 1{\text{.}}01 \times {{10}^5} \times 2.00 \times {{10}^3}}}{{8{\text{.}}31 \times 298}}\)

A

This question may have appeared a little more daunting than usual; it required candidates to think clearly about the units and carry out dimensional analysis. Answers A and D were each chosen by about 40% of the candidates.