Thermodynamics Question 3
Question 3 - 2024 (27 Jan Shift 1)
If three moles of an ideal gas at $300 K$ expand isotherrnally from $30 dm^{3}$ to $45 dm^{3}$ against a constant opposing pressure of $80 kPa$, then the amount of heat transferred is _______ J.
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Answer (1200)
Solution
Using, first law of thermodynamics,
$\Delta U=Q+W$,
$\Delta U=0$ : Process is isothermal
$Q=-W$
$W=-P _{\text {ext }} \Delta V:$ Irreversible
$=-80 \times 10^{3}(45-30) \times 10^{-3}$
$=-1200 J$
