Question

Which of following statement (s) is true

I – Slope of isotherm at critical point is maximum.

II – Larger is the value of TC easier is the liquification of gas.

III – Vander waals equation of state is applicable below critical temperature at all pressure.

• A. Only I
• B. I& II
• C. II & III
• D. only II

Answer 1

Answer: (B)

I& II

Answer 2

I – Slope of isotherm below critical point < 0.

Slope of isotherm above critical point < 0.

Slope of isotherm at critical point = 0.

So slope of isotherm at critical point is maximum.

II – TC = $\frac { 8 \mathrm { a } } { 27 \mathrm { Rb } }$

TC $\propto$ a

Larger value of TC It means less decreases in temperature is required to liquifly the gas. Gas will liquify at higher temperature. So, easier'll be liquification.

III – When gas is below critical temperature. It is 'liquid' so vander waal equation of state is not valid.

So, Answer (2).