Physics 9702 · AS & A Level · Kinetic theory of gases
Kinetic theory of gases — practice question
An ideal gas with a fixed mass is held at a temperature of $21\,^{\circ}\text{C}$. Its pressure is $2.3 \times 10^5\,\text{Pa}$ and its volume is $3.5 \times 10^{-3}\,\text{m}^3$.
(a(i))[2]
Determine the number $N$ of molecules in the gas.
(a(ii))[2]
Each molecule of the gas has mass $40\,\text{u}$. Find the root-mean-square (r.m.s.) speed of the gas molecules.
(b)[2]
The gas temperature is raised by $84\,^{\circ}\text{C}$. Find the value of the ratio $\frac{\text{new r.m.s. speed of molecules}}{\text{original r.m.s. speed of molecules}}$.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Applies $pV = NkT$ or $pV = nRT$ and $N = nN_A$” …