How much heat is given off when 64 g liquid methanol at its freezing point changes to solid methanol?

= 6.32 Joules

Explanation:

The heat given off by a substance while changing from liquid state to solid state without change in temperature is given by the formula;

Q = n×Lf

where, Q is the heat quantity, n is the number of moles and Lf is the molar heat of fusion. The methanol HF is 3.16 kJ/mol.

The number of moles = 64 g/32 g/mol

                                   = 2 moles

Therefore;

Heat = 2 moles × 3.16 kJ/mol

        = 6.32 Joules