Question

Van der Waal's equation for a gas is stated as, $p = \frac{nRT}{V-nb}-a\left(\frac{n}{V}\right)^{2}.$ This equation reduces to the perfect gas equation, $p = \frac{nRT}{V}$ when ,

• A. temperature is sufficiently high and pressure is low
• B. temperature is sufficiently low and pressure is high
• C. both temperature and pressure are very high
• D. both temperature and pressure are very low

Answer 1

Answer: (A)

temperature is sufficiently high and pressure is low

Answer 2

Van der waal equation:
$\left(p+\frac{a n^{2}}{v^{2}}\right)(v-n b)=n R T$
or,
$P=\frac{n R T}{v-n b}-a\left(\frac{n}{v}\right)^{2}$
where, v is volume
$P$ is pressure
$T$ is Temperature
$n$ is mole of gas
$R$ is universal gas constant.
the ideal gas equation works well when intermolecular attractions between gas molecular are negligible and the gas molecules themselves do not occupy a significant part of the whole volume. This is usually true when the pressure is low and the temperature is high.