Consider the following liquid-vapour equilibrium.
liquid `hArr` vapour
which of the following relations is correct-

Options

A. `(dlnP)/(dT^(2))=-(DeltaH_(v))/(T^(2))`
B. `(dlnP)/(dT)=(DeltaH_(v))/(RT^(2))`
C. `(dlnG)/(dT^(2))=(DeltaH_(v))/(RT^(2))`
D. `(dlnP)/(dT)=-(DeltaH_(v))/(RT)`

Answer

B

Explanation

For liquid vapour equilibrium, the relationship between equilibrium pressure (P), heat of vaporisation `(DeltaH_(v))` and temperature (T) will be-
ln `P=-(DeltaH_(v))/(RT)+Z` (Z=constant)
Differentiating the equation with respect to T, we get,
`(dlnP)/(dT)=(DeltaH_(v))/(RT^(2))`.