Question

Assertion: At critical point the densities of substance in gaseous and liquid states are same.
Reason: Critical temperature is the temperature at which the real gas exhibit ideal behaviour for considerable range of pressure.

<!--td {border: 1px solid #cccccc;}br {mso-data-placement:same-cell;}--> AIIMS 2013

• A. Both assertion and reason are true and reason is the correct explanation of assertion.
• B. Both assertion and reason are true but reason is not the correct explanation of assertion.
• C. Both assertion and reason are false.
• D. Assertion is true but reason is false.

Answer 1

The correct option is D Assertion is true but reason is false.

Temperature at which the real gas exhibits ideal behaviour for considerable range of pressure is known as Boyle's temperature. $T_b=\frac{a}{bR}$
Where, a and b are van der Waals constants.
Critical temperature is the temperalure above which the gas cannot be liquified, how so ever high pressure may be applied:
$T_c=\frac{8a}{27Rb}$
At the critical point, the densities of substance in gaseous and liquid state are same.
Hence, option (c) is correct.