Calculate the heat energy released when 16.8 g of liquid mercury at 25.00 °C is converted to solid mercury at its melting point.

Question

Constants for mercury at 1 atm

heat capacity of Hg(l) 28.0 J/(mol⋅K)

melting point 234.32 K

enthalpy of fusion2.29 kJ/mo

Answer 1

First we need to determine the heat released when the mercury is cooled to 234.32K. The heat released is given by Q = C_L x m x ΔT where C_L is the heat capacity of liquid mercury, m is the mass of mercury in moles, and ΔT is the difference in temperature in degrees Kelvin.

Substituting the given quantities: Q₁ = 28.0 J/mol-K x 16.8 g/200.59 g/mol x (63.7 K) = 149.4 J.

Now calculate the heat released freezes: Q₂ = 2.29 kj/mol x 16.8g /200.59 g/mol = 0.192 kj

The total heat released is 149 J+ 192 J = 341 Joules