The heat required to melt one mole of a substance is known as its molar enthalpy of fusion, denoted as Δ Hfus. For sodium chloride, Δ Hfus is 30.4 kJ/mol.
The entropy change at the melting point is given by Δ S = TmΔ HfusWhere Tm is the melting point in Kelvin. Substituting the given values, we get:
28.4 J/K/mol = Tm30.4 kJ/mol
Solving for Tm, we get:
Tm = 28.4 J/K/mol30.4 kJ/mol = 1070.4 K
Rounding off to the nearest integer, the melting point of sodium chloride is 1070 K.