The volume of a gas decreases from `500 c c` to `300 c c` when a sample of gas is compressed by an average pressure of 0.6 atm. During this process 10 J of heat is liberated. The change in internal energy is

Options

A. `-2.16 J`
B. `12.156J`
C. `2.16J`
D. `101.3 J`

Answer

C

Explanation

Here: Change in Volume (V) = 500 - 300 = 200cc = 0.2 litre, Pressure (P) = 0.6 atm and heat liberated (q) = 10J Work done (W) `= P Delta V = (0.2 xx 0.6) = 0.12` litre - atm But 1litre - atm = 101.3J.
hence W = `0.12 xx 101.3 = 12.156J`. We also know that heat is liberated, therefore it would be negative. Thus change in `Delta E = 9+W = -10 +12.16 = 2.16J`.