Question

The latent heat of vaporisation of water is 2240 J. If the work done in the process of vaporisation of 1 g is 168 J, the increase in internal energy is

• A. 1408 J
• B. 2072 J
• C. 2208 J
• D. 2408 J

Hint:

Remember that the increase in internal energy is the sum of the latent heat of vaporisation and the work done during the vaporisation process.

Answer 1

The Correct Option is B

Latent heat of vaporization of water (L) = 2240 J/g
Mass of water vaporized (m) = 1 g
Work done in the process of vaporization (W) = 168 J

We need to find the increase in internal energy (ΔU).

The heat supplied to vaporize 1 g of water is given by the latent heat of vaporization.
Heat supplied (Q) = m × L
Q = 1 g × 2240 J/g
Q = 2240 J

According to the first law of thermodynamics, the heat supplied to a system is used to increase its internal energy and to do work on the surroundings.
The first law of thermodynamics equation is:
Q = ΔU + W

Where:
Q is the heat supplied to the system
ΔU is the increase in internal energy of the system
W is the work done by the system

We are given Q = 2240 J and W = 168 J. We need to find ΔU.
Rearranging the equation to solve for ΔU:
ΔU = Q - W

Substitute the given values:
ΔU = 2240 J - 168 J
ΔU = 2072 J

Therefore, the increase in internal energy is 2072 J.

Final Answer: The final answer is 2072 J