Choose the correct statement for the work done in the expansion and heat absorbed or released when 5 litres of an ideal gas at 10 atmospheric pressure isothermally expands into vacuum until volume is 15 litres :
- Both the heat and work done will be greater than zero
- Heat absorbed will be less than zero and work done will be positive
- Work done will be zero and heat will also be zero
- Work done will be greater than zero and heat will remain zero
Answer
(3) Work done will be zero and heat will also be zero
Solution
Expansion into vacuum is free expansion: pext = 0
w = -pext V = 0
For an ideal gas at constant temperature, U = 0.
U = q + w
q = U - w = 0
Work done and heat are both zero.
Answer: (3)