Question

Calculate the amount of heat required to convert 4 kg water at 100^ centigrade into steam

Answer 1

For this question, we need to consider the Latent Heat of Vaporisation.

The amount of heat required to convert one gram of liquid into gaseous substance is called latent heat is vaporisation.


For water, this latent heat is 540 cal/g

Latent Heat of Vaporisation = Lv = 540 cal/g = 540 kcal/kg ≈ 2260 kJ/kg

(As 1 cal ≈ 4.2 J)

Now, mass m = 4 kg

Let the heat required be Q.

So, Q = m×Lv
So, Q = 4×2260 kJ
So, Q = 9040 kJ

Thus the amount of heat required to 4 kg water at 100°C into steam is 9.04 MJ ( megajoules )