A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of $37.0^{\circ} \mathrm{C}$. As it does so, it absorbs 208J of heat. The values of q and w for the process will be: ( $\mathrm{R}=8.314 \mathrm{~J} / \mathrm{mol} \mathrm{K}$ ) ( $\ell$ n $7.5=2.01$ )

(D) $\mathrm{q}=+208 \mathrm{~J}, \mathrm{w}=-208 \mathrm{~J}$

(A) $\mathrm{q}=-208 \mathrm{~J}, \mathrm{w}=-208 \mathrm{~J}$

(B) $\mathrm{q}=-208 \mathrm{~J}, \mathrm{w}=+208 \mathrm{~J}$

(C) $q=+208 \mathrm{~J}, w=+208 \mathrm{~J}$

JEE Main · 2013 · 07 Apr 2013 · Offline · Chemical Thermodynamics

A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of

37. 0^{\circ} C

. As it does so, it absorbs 208J of heat. The values of q and w for the process will be: (

R = 8.314 J / mol K

) (

ℓ

7.5 = 2.01

)

Answer: (D)

For an isothermal change of an ideal gas the internal energy does not move,

Δ U = 0

, so the first law collapses to

q = - w

. The gas takes in

208 J

of heat, giving

q = + 208 J

, and since it spends that energy doing expansion work on the surroundings,

w = - 208 J

JEE Main · 2013 · 07 Apr 2013 · Offline · Single correct option