Question

Identify the correct variation of pressure and volume of a real gas (A) and an ideal gas (B) at constant temperature.
(\(y=P;\;x=V\))

• A. Graph 1
• B. Graph 2
• C. Graph 3
• D. Graph 4

Hint:

At constant temperature: \[ PV=\text{constant} \] for an ideal gas. Real gases generally show lower pressure than ideal gases due to intermolecular attractions.

Answer 1

The Correct Option is C

Step 1: Recall Boyle’s law for an ideal gas.
For an ideal gas at constant temperature, \[ PV=\text{constant} \] Hence, \[ P\propto \frac{1}{V} \] So, the graph between pressure and volume is a rectangular hyperbola.

Step 2: Behaviour of a real gas.
Real gases deviate from ideal behaviour because of intermolecular forces and finite molecular size.
At moderate pressure, attractive forces dominate and the pressure of a real gas becomes slightly less than that of an ideal gas for the same volume.
Therefore, the real gas curve lies below the ideal gas curve.

Step 3: Identify the correct graph.
In the given options: \[ A=\text{Real gas} \] and \[ B=\text{Ideal gas} \] The correct graph should show:

• Both curves as hyperbolas

• Real gas curve below the ideal gas curve
Only graph (3) satisfies these conditions.

Step 4: Final conclusion.
Therefore, the correct variation is represented by \[ \boxed{\text{Graph 3}} \]