CAIE A-Level Physics 15.1.1 Amount of Substance

Practise identifying amount of substance as an SI base quantity and using the mole, mol, correctly in physical calculations.

Exam points

state that amount of substance is an SI base quantity with unit mol

[Maximum number: 3]

A fixed mass of an ideal gas has volume $210 \mathrm{~cm}^{3}$ at pressure $3.0 \times 10^{5} \mathrm{~Pa}$ and temperature 270 K . The volume of the gas is reduced at constant pressure to $140 \mathrm{~cm}^{3}$ , as shown in Fig. 2.1.

Fig. 2.1

The final temperature of the gas is T.

Determine:

the amount of gas
amount = mol

p V=n R T

C1

$n=\left(3.0 \times 10^{5} \times 210 \times 10^{-6}\right) /(8.31 \times 270)$

C1

$=0.028 \mathrm{~mol}$

A1

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15.1.1—Amount of substance is an SI base quantity with the base unit mol question 1