Question

Which of the following is correct statement for an ideal gas?

• A. When temperature increases, average speed decreases
• B. Mean free path decreases by increasing temperature at constant pressure
• C. If all gas molecules are assumed to be rigid sphere of negligible volume, the only possible molecular motion is translation
• D. Kinetic energy decreases by increasing pressure at constant temperature

Answer 1

The correct option is C If all gas molecules are assumed to be rigid sphere of negligible volume, the only possible molecular motion is translation

(A) If the temperature increases, average speed increases.

(B) For an ideal gas, if the temperature increases at constant pressure the gas expands and the molecules of gases move far apart from each other i.e., the mean free path increases. Hence, option B is wrong.

(C) If all gas molecules are assumed to be rigid sphere of negligible volume, the only possible molecular motion is translation. Hence, statement (C) is correct.
(D) For an ideal gas, the average kinetic energy is dependent only on temperature, for isothermal change in pressure, the average kinetic energy would not change. Hence, statement D is wrong.