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.