For chromium, Cr, the heat of fusion at its normal melting point of 1860 °C is 14.6 kJ/mol.

Question

For chromium, Cr, the heat of fusion at its normal melting point of 1860 °C is 14.6 kJ/mol.

The entropy change when 1.61 moles of solid Cr melts at  1860 °C, 1 atm is _____ JK^-1.

Answer 1

Gibbs free energy relates the enthalpy and entropy of a system:

ΔG = ΔH - TΔS

At equilibrium (in this case, at the melting point), ΔG = 0. So, since the temperature and ΔH of fusion are specified, we can solve for the ΔS of fusion:

ΔH = TΔS

This will give units of J/mol K. You can find the total entropy change by simply multiplying by the number of moles.