Heat of Vaporization Formula

The amount of heat that must be absorbed at a fixed temperature to evaporate a specific amount of liquid is called the heat of vaporization.  When the velocity of the steam and the energy of motion of the fluid are matched, the velocity of the vapor is shown to be greater.

To put it another way, the heat of vaporization is the total amount of heat necessary to transform a specific amount of liquid into vapor while maintaining the fluid’s temperature.

Formula

The heat of vaporization can be calculated as the ratio of heat require to vaporize to the mass of the given substance. It is expressed mathematically as follows:

H_v = q/m

where,

• q refers to the amount of heat
• m refers to the substance’s mass

Sample Questions

Question 1. Find the heat of vaporization to vaporize 200 g of H2O, if the total amount of heat required to do it is 2800 J.

Solution:

Given: m = 200 g and q = 2800 J

Since, Hv = q/m

= 2800/200

= 14 J/g

Question 2. Find the heat of vaporization to vaporize 100 g of liquid, if the total amount of heat required to do it is 1400 J.

Solution:

Given: m = 100 g and q = 1500 J

Since, Hv = q/m

= 1500/100

= 15 J/g

Question 3. Find the heat of vaporization to vaporize 25 g of liquid, if the total amount of heat required to do it is 56425 J.

Solution:

Given: m = 25 g and q = 56425 J

Since, Hv = q/m

= 56425/25

= 2257 J/g

Question 4. Find the heat energy required to vaporize 45 g of a liquid if the heat of vaporization is 56455 J/g.

Solution:

Given: m = 45 g and Hv = 56455 J/g

Since, Hv = q/m ⇒ q = Hv x m

= 56455 x 45

= 2540475 J

Question 5. Find the heat energy required to vaporize 69 g of a liquid if the heat of vaporization is 333 J/g.

Solution:

Given: m = 69 g and Hv = 333 J/g

Since, Hv = q/m ⇒ q = Hv x m

= 69 x 333

= 22977 J