Question

An electric current of 0.50A from a 12V supply is passed for 300 sec through a resistance in thermal contact with water and the water is allowed to boil under a pressure of 1.0 atm. The value of enthalpy change during the process, if 0.798 gm of water is vaporised, will be :

• A. $-44 \text{ kJ mol}^{-1}$
• B. $+41 \text{ kJ mol}^{-1}$
• C. $-37 \text{ kJ mol}^{-1}$
• D. $+82 \text{ kJ mol}^{-1}$

Hint:

Pay close attention to thermodynamic signs! Vaporization, melting, and sublimation are always endothermic (positive $\Delta H$). Condensation and freezing are always exothermic (negative $\Delta H$). This immediately eliminates options with negative signs for boiling processes.

Answer 1

The Correct Option is B