Questions
Question 1
*
Find \(v_{\mathrm{rms}}\) for a gas with \(M=2.0\times10^{-2}\,\mathrm{kg\,mol^{-1}}\) at \(300\,\mathrm{K}\).
Question 2
*
For a Maxwell-Boltzmann speed distribution, order \(v_{\mathrm{mp}}\), \(\bar v\), and \(v_{\mathrm{rms}}\) from smallest to largest.
Question 3
*+
If a gas temperature is increased from \(300\,\mathrm{K}\) to \(1200\,\mathrm{K}\), by what factor does \(v_{\mathrm{rms}}\) change?
Question 4
**
Find the most probable speed of nitrogen at \(300\,\mathrm{K}\), using \(M=2.8\times10^{-2}\,\mathrm{kg\,mol^{-1}}\).
Question 5
**
Find the mean speed of helium at \(300\,\mathrm{K}\), using \(M=4.0\times10^{-3}\,\mathrm{kg\,mol^{-1}}\).
Question 6
**+
At the same temperature, gas A has molar mass \(M\) and gas B has molar mass \(9M\). Find \(\bar v_A/\bar v_B\).
Question 7
***
A gas has molecular radius \(1.5\times10^{-10}\,\mathrm{m}\) and number density \(2.5\times10^{25}\,\mathrm{m^{-3}}\). Estimate its mean free path using \(\lambda=1/[4\sqrt2\pi r^2(N/V)]\).
Question 8
***
A molecule has mean free path \(8.0\times10^{-8}\,\mathrm{m}\) and speed \(500\,\mathrm{m\,s^{-1}}\). Estimate its mean free time.
Question 9
***+
Explain why \(v_{\mathrm{rms}}\) is more directly connected to average kinetic energy than the mean speed \(\bar v\).
Question 10
****
A gas is compressed isothermally so its number density doubles. In the hard-sphere model, derive how the mean free path and mean free time change, assuming the characteristic molecular speed is unchanged.
Question 11
****
At what temperature would helium \((M=4.0\times10^{-3}\,\mathrm{kg\,mol^{-1}})\) have the same \(v_{\mathrm{rms}}\) as nitrogen \((M=2.8\times10^{-2}\,\mathrm{kg\,mol^{-1}})\) at \(300\,\mathrm{K}\)?
Question 12
****+
For nitrogen at \(300\,\mathrm K\), compare \(v_{\mathrm{mp}}\), \(\bar v\), and \(v_{\mathrm{rms}}\) using their formula factors.
Question 13
****+
A gas has mean free path \(1.2\times10^{-7}\,\mathrm m\) and mean speed \(480\,\mathrm{m\,s^{-1}}\). Estimate the collision frequency.
Question 14
****+
A gas expands isothermally to four times its original volume with the same number of molecules. How do mean free path and mean free time change?
Question 15
****+
A gas has molecular radius doubled while number density and temperature stay fixed. In the hard-sphere model, how does mean free path change?
Question 16
*****
Derive \(v_{\mathrm{rms}}=\sqrt{3RT/M}\) from \(\langle K_{\mathrm{tr}}\rangle=3k_BT/2\).
Question 17
*****
Explain why the Maxwell-Boltzmann distribution broadens and shifts right as temperature increases.
Question 18
*****
A gas mixture contains helium and argon at the same temperature. Explain why their speed distributions are different but their average translational kinetic energies are the same.
Question 19
*****
Derive the dependence of mean free path on pressure for an ideal gas at fixed temperature and molecular radius.
Question 20
*****
Why is \(v_{\mathrm{rms}}\) not the same as the speed of every molecule, and why is that distinction important?