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Work done in Isothermal Irreversible Process

One kg of air...

Question

One kg of air, initially at a temperature of $127^{0} C$ , expands reversibly at a constant pressure until the volume is doubled. If the gas constant of air is 287 J/kg. K, the magnitude of work transfer is kJ (round off to 2 decimal places).
114.8

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Solution

The correct option is A 114.8

$m = 1 k g; T_{1} = 127^{0} C = 400 k$
$P = C; V_{2} = 2 V_{1}; R = 0.287 k J / k g K$
$W = P_{1} (V_{2} - V_{1})$
$= P_{1} (2 V_{1} - V_{1})$
$= P_{1} . V_{1} = m R T_{1}$
$= 1 \times 0.287 \times 400$
$= 114.8 k J$

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