IB Chemistry SL 1.5.4 Ideal Gas Equation Question Bank

Practise IB Chemistry SL 1.5.4 with questions applying PV=nRT while converting pressure, volume and temperature units.

Exam points

convert temperature to kelvin and align pressure and volume units before using PV = nRT
rearrange the ideal-gas equation to calculate amount, molar mass, pressure or volume
apply a gas percentage or changed conditions before evaluating the required quantity

[Maximum number: 3]

A hydrocarbon has the empirical formula $\mathrm{C}_{3} \mathrm{H}_{7}$ . When 1.17 g of the compound is heated to $85^{\circ} \mathrm{C}$ at a pressure of 101 kPa it occupies a volume of $400 \mathrm{~cm}^{3}$ .

Calculate the molar mass of the compound, showing your working.

$T=85+273=358\ \mathrm{K}$ $n=\frac{pV}{RT} =\frac{101\times0.400}{8.31\times358} =0.0136\ \mathrm{mol}$ $M=\frac{m}{n} =\frac{1.17}{0.0136} =86.2\ \mathrm{g\ mol^{-1}}$

Award [1 max] for correct final answer without working.

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1.5.4—Ideal gas equation question 1