Question
Chemistry Question on Thermodynamics
Under isothermal conditions a gas expands from 0.2 dm3 to 0.8 dm3 against a constant pressure of 2 bar at 300 K. Find the work done by the gas.(1 dm3 bar = 100 J)
A
160 J
B
–120 J
C
–40 J
D
20 J
Answer
–120 J
Explanation
Solution
The work done by a gas during expansion or compression:
Work = - PΔV
Here,
ΔV = final volume - initial volume
ΔV = 0.8 dm³ - 0.2 dm³
ΔV = 0.6 dm³
The pressure (P) is given as 2 bar, which we can convert to the corresponding units of dm³ bar:
1 dm³ bar = 100 J
So, 2 bar = 200 J.
Substituting the values into the formula, we get:
Work = - PΔV
Work = -(200 J) x (0.6 dm³)
Work = -120 J
Therefore, the work done by the gas is -120 J, which matches option (B) in the given choices.