Question
What are ideal and real gases? Give the points of difference between them.
Solution
Ideal gases: A gas which obeys the general gas equation and other gas laws under all conditions of temperature and pressure is known as an ideal gas or perfect gas.
Characteristics of an ideal gas: The molecules of an ideal gas
(i) occupy a negligible volume
(ii) have no intermolecular attractive forces.
Characteristics of an ideal gas: The molecules of an ideal gas
(i) occupy a negligible volume
(ii) have no intermolecular attractive forces.
Real gases: A gas which does not obey general gas equation and all other gas laws strictly but tends towards ideality at low pressure and high temperature is known as real gas or non-ideal gas.
Points of differences:
| Ideal gas | Real gas |
| 1. It obeys gas laws (PV = RT) under all conditions of temp, and pressure. | 1. It obeys gas laws only at high temp. and low pressure. |
| 2. It does not exist in actual practice. The concept of an ideal gas is only hypothetical. | 2. All gases are real gases. |
| 3. The volume occupied by molecules is negligible as compared to the total volume of gas. | 3. The volume occupied by molecules is not negligible. |
| 4. There are no intermolecular forces of attraction or repulsion among the molecules. | 4. There are intermolecular forces of attraction due to which the pressure exerted is less than that calculated from gas laws. |
