Question

The work done during reversible isothermal expansion of one mole of hydrogen gas at 25oC from a pressure of 20 atm to 10 atm is:
(Given R = 2.0 cal K-1 mol-1)

• A. 0 calorie
• B. -413.14 calories
• C. 413.14 calories
• D. 100 calories

Answer 1

Answer: (B)

-413.14 calories

Answer 2

1. For isothermal expansion, work done is calculated as:

$W = -nRT \ln \frac{P_2}{P_1}$

2. Substituting the given values:

$W = -(1) \times (2.0) \times (298) \times \ln \left(\frac{10}{20}\right)$

3. Simplify:

$W = -596 \times \ln(0.5) = -596 \times (-0.693) \approx -413.14 \text{ calories}$.