Find the work done by 0.5 text moles of an ideal monoatomic gas when it is heated at a constant pressure of 1 text atm from 20^circtext C to 90^circtext C . (Take R = 8.31 text J/mol cdottext K )

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EEJ MAIN Physics QUESTION #7056

Question 1

Find the work done by $0.5 \text{ moles}$ of an ideal monoatomic gas when it is heated at a constant pressure of $1 \text{ atm}$ from $20^\circ\text{C}$ to $90^\circ\text{C}$. (Take $R = 8.31 \text{ J/mol}\cdot\text{K}$)

$581 \text{ J}$
$291 \text{ J}$✔️
$146 \text{ J}$
$73 \text{ J}$

Correct Answer Explanation

Work done at constant pressure is given by $W = P \Delta V$.

Using the ideal gas law ($PV = nRT$), at constant pressure, $P \Delta V = n R \Delta T$.

$W = 0.5 \times 8.31 \times (90 - 20)$

$W = 0.5 \times 8.31 \times 70 = 35 \times 8.31 = 290.85 \text{ J}$.

Rounding gives approximately $291 \text{ J}$.

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