CAIE A-Level Physics 15.1.2 Molar Quantities and Avogadro Constant

Practise using Avogadro’s constant to relate moles, particles and molar quantities, calculating N = nNA and checking substance units.

Exam points

use the Avogadro constant to relate one mole to the number of particles in a sample
calculate amount of substance, number of particles or molar quantities using N = nN_A
interpret particle counts and units in a stated substance or gas problem

[Maximum number: 1]

A sealed vessel contains a mass of 0.0424 kg of an ideal gas at $227^{\circ} \mathrm{C}$ . The pressure of the gas is $1.37 \times 10^{5} \mathrm{~Pa}$ and the volume of the gas is $0.640 \mathrm{~m}^{3}$ .

Calculate:

the mass of one molecule of the gas

mass =kg [1]

mass $=0.0424 /\left(1.27 \times 10^{25}\right)$ $=3.34 \times 10^{-27} \mathrm{~kg}$

A1

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15.1.2—Molar quantities where one mole of any substance is the amount containing a question 1