A 7 kg sample of mercury is completely solidified and liberates 81.06 kJ of energy.What is the original temperature of the mercury? (The melting point of mercury is 234 K,the heat of fusion of mercury is 11.3 kJ/kg,and the specific heat of mercury is 140 J/kg·K. )
A)240 K
B)580 K
C)2.0 K
D)850 K

Question

Quizplus · Accepted Answer

The energy liberated during solidification is used to cool the mercury to its melting point and then solidify it. First, calculate the energy required to solidify the mercury: 7 kg * 11.3 kJ/kg = 79.1 kJ. The remaining energy (81.06 kJ - 79.1 kJ = 1.96 kJ) is used to cool the mercury. Using the specific heat formula, 1.96 kJ = 7 kg * 140 J/kg·K * (T - 234 K), solve for T to find the original temperature.

A 7 Kg Sample of Mercury Is Completely Solidified and Liberates