Which sample of oxygen gas contains molecules with the smallest average speed?

A)

The sample of oxygen gas which is at 250 Kelvin temperature contains molecules with the smallest average speed.

Explanation:

According to the kinetic molecular theory of gases:

The kinetic energy of a gas is a measure of its Kelvin temperature. Individual gas molecules have different speeds, but the temperature and kinetic energy of the gas refer to the average of these speeds.

The average kinetic energy of a gas particle is directly proportional to the temperature. An increase in temperature increases the speed in which the gas molecules move.

Considering different samples of oxygen gas at different temperatures, each have different kinetic energies. The sample at lowest temperature will have the lowest kinetic energy and thus the smallest average speed.

4 Sample D

A. 1.73 x 10^5 J

Explanation:

The internal energy of a gas is related to the average speed of the molecules of the gas. In fact:

- The internal energy, U, is directly proportional to the temperature of the gas, T, according to

[tex]U=\frac{3}{2}nRT[/tex]

- The temperature of the gas, T, is proportional to the square of the average speed of the molecules, v, according to

[tex]\frac{3}{2}kT=\frac{1}{2}mv^2[/tex]

where both terms represent the average kinetic energy of the molecules.

- Therefore, we can conclude that the higher the internal energy, the faster the average speed of the molecules: among the choices given, the sample with highest internal energy is sample A.

Sample d with a temperature of 298 K