Question

When 1mole gas is heated at constant volume, temperature is raised from 298-308K Heat supplied to the gas is 500J Then which is correct?
a)q=w=500, dU=0
b) q=dU =500 w=0
c) q=w=500 dU not equal to 0
d) q=w=500J dU =0

Answer 1

Ans b is correct....
from first law of thermodynamics at constant volume (dQ)v=du=500J W= q-o=0

Answer 2

Answer: b) q= dU =500 w=0

Explanation:

According to first law of thermodynamics:

$\Delta U=q+w$

$\Delta U$=Change in internal energy

q = heat absorbed or released  

w = work done or by the system

w = work done by the system=$-P\Delta V$  

q = + 500J   {Heat absorbed by the system is positive}

w = 0  (as volume is constant, $\Delta V=0$

$\Delta U=500+0$

$\Delta U=500J$

Thus heat and internal energy are 500 joules and work done is zero.