Question

The mass of 5.6 ${\mathrm{dm}}^3$ of a certain gas at STP is 12.0 g. Calculate the relative molecular mas of the gas.

Answer 1

Step 1: Mass of 5.6 ${\mathrm{dm}}^3$ of a certain gas a S.T.P = 12 g

Step 2:No. of moles $=\frac{\mathrm{Volume}\mathrm{at}\mathrm{S}.\mathrm{T}.\mathrm{P}}{22.4}$

Step 3:Volume at STP $=\frac{\mathrm{Mass}}{\mathrm{Molecular}\mathrm{weight}}\times 22.4$

Molecular weight $=\frac{12}{5.6}\times 22.4$

$=48\mathrm{g}/\mathrm{mole}$

Therefore, relative molecular mass of gas is 48g /mole.