Question

a 1 l sample of helium gas at 25 °c and 1 atm is combined with a 1 l sample of neon gas at 25 °c and 1 atm. the temperature is kept constant. which of the following statements about combining the gases is correct? a the average speed of the helium atoms increases when the gases are combined. b the average speed of the neon atoms increases when the gases are combined. c the average kinetic energy of the helium atoms increases when the gases are combined. d the average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.

Explanation:

Step1: Recall kinetic - theory relation

The average kinetic energy of gas particles is given by $KE_{avg}=\frac{3}{2}kT$, where $k$ is the Boltzmann constant and $T$ is the temperature.

Step2: Analyze the given condition

The temperature is kept constant ($T = 25^{\circ}C$) when the helium and neon gases are combined. Since $KE_{avg}$ depends only on temperature for an ideal gas, and $T$ is unchanged, the average kinetic energy of both helium and neon atoms remains the same. Also, the average speed of gas particles is related to temperature and molar - mass ($v_{avg}=\sqrt{\frac{8RT}{\pi M}}$), and since $T$ is constant, the average speeds of helium and neon atoms do not change due to combination.

Answer:

D. The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.