What is the entropy change of the system when 17.5 g of liquid benzene (c6h6) evaporates at the normal boiling point? the normal boiling point of benzene is 80.1°c and δhvap is 30.7 kj/mol?

Answer : The entropy change of the system is, 19.5 J/K

Solution :

Formula used :

or,

where,

= entropy change of the system = ?

= enthalpy of vaporization = 30.7 kJ/mole

n = number of moles of benzene

w = mass of benzene = 17.5 g

M = molar mass of benzene = 78 g/mole

= normal boiling point of benzene =

Now put all the given values in the above formula, we get the entropy change of the system.

Therefore, the entropy change of the system is, 19.5 J/K