Question

How many calories are released when 6 grams of 100°C steam turns to 0°C ice?

Answer 1

Answer: 4276.2 calories

Explanation:

Given

mass of steam is 6 gm at $100^{\circ}C$

Conversion of steam to ice involves

• steam to water at $100^{\circ}C$

• water at $100^{\circ}C$ to water at $0^{\circ}C$

• water to the ice at $0^{\circ}C$

Calories released during the conversion of steam to water at $100^{\circ}C$

$E_1=mL_v\quad [L_v=\text{latent heat of vaporisation}]\\E_1=6\times 533=3198\ cal.$

Calories released during the conversion of water at $100^{\circ}C$ to water at $0^{\circ}C$

$E_2=mc(\Delta T)\quad [c=\text{specific heat of water,}1\ cal./gm.^{\circ}C]\\E_2=6\times 1\times 100=600\ cal.$

Calories released during the conversion of water to the ice at $0^{\circ}C$

$E_3=mL_f\quad [L_f=\text{latent heat of fusion}]\\E_3=6\times 79.7=478.2\ cal.$

The total energy released is

$E=E_1+E_2+E_3\\E=3198+600+478.2=4276.2\ cal.$