Question

A real gas behaves like an ideal gas if its,
     A. Pressure and temperature are both high.
     B. Pressure and temperature are both low.
     C. Pressure is high and temperature is low.
     D. Pressure is low and temperature is high.

Answer 1

Hint: To solve this question, we will use kinetic theory of gases which gives an idea about ideal gas and real gas. Due to many assumptions made in the postulates of kinetic theory of gases, the real gas deviates from the ideal gas but they behave the same in some particular temperature and pressure conditions.

Complete answer:
Before discussing the condition when real gas behaves like an ideal gas, let us understand what are the assumptions made in postulates of kinetic theory of gases about these gases.
There are two main assumptions regarding the deviation of real gases from ideal gas behavior. They are,
1. Compared to the volume of the vessel, the volume of the gas particle is negligible.
     But, in case of a real gas, the volume of every individual gas particle is very significant.
2. There is no interaction between the gaseous particles.
    In a real gas, there are forces of attraction between the molecules.
So, these assumptions are contradictory.
Now, we know that, ideal gas equation is given as,
$PV=nRT$
Where, P is the pressure of the gas.
              V is the volume taken up by the gas.
              T is the temperature of the gas.
              R is the gas constant.
     And n is the number of moles of the gas.
From this, we can understand that if the pressure of the gas is too high, or the temperature is too low, there will be a substantial deviation in the ideal gas equation. So, a real gas obtains ideal gas behavior at very low pressure and high temperature.

Therefore, option D is correct.

Note:
We must know that an ideal gas is a fictional gas which was conceived by scientists so that it would be far simpler to explain the basic ideal gas law. Ideal gas particles are supposed to be point masses that travel in continuous, spontaneous, straight line motion. Its behavior is defined in the kinetic –molecular theory of gases by the assumptions stated in solution.