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One mole of an ideal gas at 27 deg C and initial pressure 8.21 atm absorbs 420 cal of heat during a reversible isothermal expansion. Calculate the final volume (in litres) of the gas. [Use R = 0.0821 L*atm/(mol*K); 1 cal = 4.18 J; 1 L*atm = 101.3 J]

1. 2.0 L
2. 4.0 L
3. 6.0 L
4. 8.0 L

Correct answer: 4.0 L

Solution

In isothermal expansion of an ideal gas, delta U = 0, so q = W = nRT*ln(V2/V1). Using V1 from PV = nRT, then 420 cal converted to L*atm units, we solve for V2.

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