Question

The specific latent heat of vaporisation of water is 2200 kJ kg, and the specific

heat capacity of water is 4200 J/ kg.K. A heating element is immersed in an
insulated cup of water. It takes five minutes to boil the water completely from an
initial temperature of 30°C. Assuming no heat is lost to the surroundings,
determine the mass of the water if the heating element is operating at 1000 W.​

Answer 1

0.12 kg

Step-by-step explanation:

The amount of energy added is:

1000 W × (5 min × 60 s/min) = 300,000 J = 300 kJ

Heat to boil the water is:

q = mCΔT + mL

q = m (CΔT + L)

300 kJ = m (4.2 kJ/kg/K × (100°C − 30°C) + 2200 kJ/kg)

300 kJ = m (2494 kJ/kg)

m = 0.12 kg