The fusion heat and the solidifitation heat have the same magnitude.
The difference is that when substances melt they are gaining (absorbing) heat and when they freeze (solidify) the loss (release) heat.
The amount of heat is 3.16 kJ/mol and you need to determine the amount of substance (methanol) that freezes.
Divide the 63 grams of CH3OH by the molar mass of CH3OH to find the number of moles of CH3OH.
Molar mass of methanol = 12 g/mol + 4*1g/mol + 16 g/mol = 32 g/mol
=> number of moles = 63 g / (32 g / mol) = 1.969 mol ≈ 2.0 mol
Now, total heat = molar specific heat * number of moles
=> total heat = 3.16 kJ/mol * 2.0 mol = 6.32 kJ
Given that the CH3OH is freezing it will release that heat, and the convention is that a heat released is considered negative.
Then, the final answer is - 6.32 kJ
