The specific heat of solid zinc is 0.39 J/goC, the melting point of zinc is 420oC, its molar heat of fusion is 7.3 kJ/mol, and the specific heat of liquid zinc is 0.51 J/goC. How much energy is required to convert 19.2 g of zinc at 20oC to liquid zinc at 535oC? Answer in kJ.

Explanation:

Using the specific heat formula, we can easily determine the energy required by any material to increase its temperature.

Q = mcΔT

Here m is given as 19.2 g of zinc, c is the specific heat capacity which is equal to 0.39 J/g°C, ΔT is the change in temperature and Q is the energy required.

Since, the initial temperature is given as 20°C and the final temperature in liquid state is given as 535 °C.

But first the solid zinc should get melted to become into liquid. Thus, the first energy is required to melt the zinc. As the melting point of zinc is given as 420 °C, this will be the final temperature of the zinc from 20°C with the specific heat value of 0.39 J/g°C.

ΔT = 420-20 = 400 °C.

Q = 19.2 × 0.39 × 400 =2.9952 kJ.

So, 2.9952 kJ of energy is required to melt the solid zinc first. Then, the specific heat of liquid zinc is given as 0.51 J/g°C to heat the liquid from 420 °C to 535 °C.

Thus, in second step, ΔT = 535 - 420 = 115 °C.

So, the energy required to increase the temperature of the liquid zinc is

Q = 19.2 * 0.51 * 115 =1.12608 kJ.

Then, the sum of both the energies will give us the total energy required to convert 19.2 g of zinc at 20 °C to liquid zinc at 535 °C.

Energy = 2.9952 + 1.12608=4.12 kJ.

Thus, the total energy required to convert 19.2 g of zinc at 20 °C to liquid zinc at 535 °C is 4.12 kJ.