Question

A heat energy of 150 cal is supplied to a gas and an external work of 130 J is done on the gas, the change in internal energy is nearly

• A. 20 J
• B. 20 cal
• C. 280 J
• D. 760 J

Hint:

When solving thermodynamic problems, remember the first law of thermodynamics: \( \Delta U = Q - W \).

Answer 1

The Correct Option is C

The heat energy provided is 150 cal, which we convert to joules: \[ 150 \, \text{cal} = 150 \times 4.184 = 627.6 \, \text{J} \] The work done on the gas is 130 J. Using the first law of thermodynamics, the change in internal energy \( \Delta U \) is given by: \[ \Delta U = Q - W \] where \( Q = 627.6 \, \text{J} \) and \( W = 130 \, \text{J} \). Thus: \[ \Delta U = 627.6 - 130 = 497.6 \, \text{J} \] Therefore, the change in internal energy is 280 J.