Asample of an ideal gas is cooled from 50.0°c to 25.0°c in a sealed container at constant volume.
which of the following values for the gas will decrease?
i. the average molecular mass of the gas
ii. the average distance between the molecules
iii. the average speed of the molecules

(a) i only
(b) ii only
(c) iii only
(d) i and iii
(e) ii and iii

Option (E) is the correct answer.

Explanation:

Since, it is given that the container is sealed one. So, no gas molecule is able to escape into the surrounding. Therefore, average molecular mass of the gas will remain the same.

Also, it is given that gas is cooled down from to . This means that there occurs a decrease in kinetic energy of the molecules of gas as kinetic energy is directly proportional to temperature.

Mathematically,      

Hence, sped of molecules will decrease and molecules become closer to each other with decrease in temperature.

Thus, we can conclude that following values for the gas will decrease.

i think it's letter a.