Question

The compressibility factor $z=\frac{PV}{nRT}$ of a gas above $T=\frac{a}{Rb}$ will be:

• A. Always less than unity
• B. Always equal to unity
• C. Always greater than unity
• D. Depends on pressure

Answer 1

The correct option is C Always greater than unity

$T=\frac{a}{Rb}$ is known as the Boyle's temperature and above Boyle's temperature, the compressibility factor is always greater than unity and increases slowly but steadily as pressure increases.
So, in real gases above Boyle's temperature, $Z>1$.