As a 7.00-kg sample of liquid mercury is cooled into a solid, it liberates 81.06 kJ of energy. What is the original temperature of the mercury?

Answer 1

You need to find specific heat of Hg (c), L_fusion of Hg, and T_MP of Hg

You then solve Q_out = -mc(T_MP-T_i) + mL_f (Q made positive for out of system - T went down, L_f is exothermic)

Make sure that the units mesh as you are unlikely to find everything KJ and Kg based.

Good luck