Answer
53.6 KJ
Explanation:
The energy released came from two discrete processes: the steam condenses to release some latent heat of condensation at 100 l o C the water cools down to 0 l o C to 100 l o C without solidfying. The amount of energy released in the first process is dependent on the L v latent heat of vaporization for water and the mass of the sample: E ( phase change ) = m ⋅ L v = 20 l g × 2 , 260 l J ⋅ g − 1 E ( phase change ) = 45 , 200 l J On the other hand, the amount of energy released in the second process depends on both the specific heat of water, the mass of the sample, and the magnitude of the change in temperature. E ( cooling ) = m ⋅ c ⋅ Δ T E ( cooling ) = 20 l g ⋅ 4.2 l J ⋅ g − 1 ⋅ K − 1 ⋅ ( 100 l K − 0 l K ) E ( cooling ) = 8 , 400 l J Taking the sum of the energy change of the two processes gives the total amount of energy released: E ( released ) = E ( phase change ) + E ( cooling ) = 53 , 600 l J = 53.6 l kJ
