Question

Consider the following statements:-
(a) At high pressure all real gases have $Z >1$ while at moderate pressure most gases have $Z < 1$
(b) Van der waal constant $'a'$ is a measure of attractive force within the gas and is independent of temperature and pressure.
(c) Greater the critical temperature of a gas, more easily it will be liquified.
(d) There is no force of attraction between molecules of ideal gas.
The correct statements are:

• A. Only $b,c,d$
• B. Only $a,c,d$
• C. Only $c,d$
• D. All $a,b,c,d$

Answer 1

Answer: (D)

(1) At high pressure, the gas molecules come close to each other and the empty space between the molecules is reduced to some extent. Therefore, the gas becomes less compressible at these higher pressures.
From the real gas equation,
$P +\frac{ an ^2}{ v ^2} V - nb = nRTAt$ high pressure
$\frac{ an ^2}{ V ^2}$ is negligible compare to P.P $V - nb = nRTZ =1+\frac{ bP }{ RT } Z >1$
As similar at moderate pressure $Z <1$
(2) Van der waal constant '$a$' is a measure of attractive force within the gas and is independent of temperature and pressure.
It is the pressure correction term.
(3) $T _{ c }=\frac{8 a }{27 Rb } a ^{\prime}$ increases ; $T _{ c }$ increases ; the rate of easility liquification increases
(4) According to the kinetic theory of gases, there is no force of attraction between molecules of ideal gas.