Thermodynamics and Thermochemistry - Result Question 1
1. An ideal gas is allowed to expand from $1 L$ to $10 L$ against a constant external pressure of 1 bar. The work done in $kJ$ is
(2019 Main, 12 April I)
(a) $-9.0$
(b) $+10.0$
(c) $-0.9$
(d) $-2.0$
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Answer:
Correct Answer: 1. (c)
Solution:
Key Idea: Work done during isothermal expansion of an ideal gas is given by the equation.
$ W=-p _{\text {ext }}\left(V _2-V _1\right) $
According to the given conditions, the expansion is against constant external pressure. So, the work done is given by following formula;
$W =-p _{\text {ext }}\left(V _2-V _1\right) $
$ =-1 \text { bar }(10 L-1 L)=-9 L \text { bar } \quad(\because 1$ $ L $ $bar=100 $ $J) $
$ =-9 \times 100 J=-0.9 $ $kJ$
BETA
