Question

The amount of heat required to change liquid water to vapor at its boiling temperature is 2256 kJ/kg. The amount of heat required to change liquid mercury to its vapor state at its boiling temperature is 295 kJ/kg. One kg of each substance is currently at its boiling point. How will the amount of thermal energy required to change each substance from a liquid to a gas differ?

Answer 1

Answer:

1961 kJ

Explanation:

Since the mass of each substance is 1 kg, the heat required to change a substance at is boiling point is its latent heat of vapourization, L. For a given mass, m, the quantity of heat Q = mL

For liquid water, m = 1 kg and L = 2256 kJ/kg.

So, quantity of heat required is thus Q₁ = 1 kg × 2256 kJ/kg = 2256 kJ

For liquid mercury, m = 1 kg and L = 295 kJ/kg.

So, quantity of heat required is thus Q₂ = 1 kg × 295 kJ/kg = 295 kJ

The amount their thermal energies differ is thus Q₁ - Q₂ = 2256 kJ - 295 kJ = 1961 kJ