Question

How much heat is given off by 5.0 g of steam at 100oC as it condenses and cools to 20oC?
a. 2.70 kcal
b. 2.80 kcal
c. 2.89 kcal
d. 3.10 kcal

Answer 1

Given:-

mass of steam, m=5 g=$5\times10^{-3}kg$

Initial temperature of steam, $T_{i}=100^{0}C$

Final temperature of water, $T_{f}=20^{0}C$

To Find:-

heat lost by the steam

Explanation:-

We know that, latent heat of vaporization of steam, L=2260 kJ/kg=540.67 kcal/kg and specific heat of water, C=4.18 kJ/kg-K=1 kcal/kg-K

$\text{Heat lost by the steam, Q}=\left(m\times L\right)+\left(m\times C\times\Delta T\right)\\\\Q=\left(5\times10^{-3}\times540.67\right)+\left(5\times10^{-3}\times1\times(100-20)\right)=3.1kcal$