Kinetic Theory of Gases: Pressure, Energy, Humidity, and Molecular Motion

All flashcards

What is Dalton’s law?

For a mixture of ideal gases, total pressure equals the sum of the component partial pressures.

What is vapor pressure?

The equilibrium partial pressure of a vapor over its condensed phase at a given temperature.

What is the dew point?

The temperature to which air must be cooled for condensation to begin.

What is rms speed?

The square root of the average of the squared molecular speeds.

What is mean free path?

The average distance a molecule travels between collisions with other molecules.

Quiz questions

1. For an isotropic ideal gas containing $N$ molecules of mass $m$, which relation connects pressure and average squared speed?Answer: $pV=\frac{1}{3}Nm\overline{v^2}$
2. What is the average translational kinetic energy per molecule of an ideal gas at absolute temperature $T$?Answer: $\overline{K}=\frac{3}{2}k_BT$
3. A mixture of ideal gases is at thermal equilibrium in one container. How is its total pressure related to the component partial pressures?Answer: The total pressure is the sum of the component partial pressures.
4. How is relative humidity calculated at air temperature $T$?Answer: $\frac{p_{\mathrm{water}}}{p_{\mathrm{vapor}}(T)}\times100\%$
5. Using rms speed as a typical molecular speed, how is mean free time $\tau$ estimated from mean free path $\lambda$?Answer: $\tau=\frac{\lambda}{v_{\mathrm{rms}}}$