JEE Main · 2011 · 10 Apr 2011 · Offline · Chemical Thermodynamics

The entropy change involved in the isothermal reversible expansion of 2 moles of an ideal gas from a volume of

10 dm^{3}

to a volume of

100 dm^{3}

2 7^{\circ} C

is :

Answer: (D)

Solution

For the isothermal reversible expansion of an ideal gas,

Δ S = n R ln \frac{V _{f}}{V _{i}}

. Here

Δ S = 2 \times 8.314 \times ln \frac{100}{10} = 2 \times 8.314 \times 2.303 \approx 38.3 J K^{- 1}

. Since this is the total entropy change for the

2

moles taken together, the correct unit is

J K^{- 1}

, not

J mol^{- 1} K^{- 1}

JEE Main · 2011 · 10 Apr 2011 · Offline · Single correct option