A liquid when kept inside a thermally insulated closed vessel at $25^{\circ} \mathrm{C}$ was mechanically stirred from outside. What will be the correct option for the following thermodynamic parameters ?

(A) $\Delta \mathrm{U}>0, \mathrm{q}=0, \mathrm{w}>0$

(D) $\Delta \mathrm{U}=0, \mathrm{q} 0$

JEE Main · 2025 · 22 Jan 2025 · Shift 1 · Chemical Thermodynamics

A liquid when kept inside a thermally insulated closed vessel at

2 5^{\circ} C

was mechanically stirred from outside. What will be the correct option for the following thermodynamic parameters ?

Answer: (A)

The vessel is thermally insulated, so no heat crosses its boundary:

q = 0

.

Mechanical stirring does work on the liquid from outside the system, and work done on the system is taken as positive:

w > 0

.

By the first law,

Δ U = q + w = 0 + w > 0

. The mechanical energy of stirring converts into the internal (thermal) energy of the liquid.

JEE Main · 2025 · 22 Jan 2025 · Shift 1 · Single correct option