Physics 9702 · AS & A Level · Kinetic theory of gases

Kinetic theory of gases — practice question

(a)[4]

State the fundamental assumptions of the kinetic theory of gases.

(b)[3]

Use the ideal-gas pressure equations to infer that the mean translational kinetic energy $\langle E_K \rangle$ of one molecule of an ideal gas is $\langle E_K \rangle = \frac{3}{2}\frac{R}{N_A}T$, where $R$ denotes the molar gas constant, $N_A$ is the Avogadro constant and $T$ is the thermodynamic temperature of the gas.

(c(i))[2]

A deuterium nucleus $^{2}_{1}\text{H}$ and a proton collide. A nuclear reaction occurs, shown by $^{2}_{1}\text{H} + ^{1}_{1}\text{p} \rightarrow ^{3}_{2}\text{He} + \gamma$. State and explain whether this reaction is nuclear fission or nuclear fusion.

(c(ii))[3]

For the reaction to proceed, the least total kinetic energy of the deuterium nucleus and the proton is $2.4 \times 10^{-14}\,\text{J}$. Assuming that a mixture of deuterium nuclei and protons behaves as an ideal gas, calculate the sample temperature needed for this reaction to occur.

(c(iii))[1]

Suggest why the assumption made in (ii) may not be valid.

(ii)[3]

For the reaction to proceed, the smallest total kinetic energy of the deuterium nucleus and the proton is $2.4 \times 10^{-14}\,\text{J}$. Assuming that a sample containing deuterium nuclei and protons behaves as an ideal gas, calculate the temperature of the sample for this reaction to occur.

(iii)[1]

Suggest why the assumption made in (ii) might not be valid.

Worked solution & mark scheme

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