Question

What is the free energy change $\left(\Delta G\right)$ when 1.0 mole of water at ${100}^{\circ }C$ and 1 atm pressure is converted into steam at ${100}^{\circ }C$ and 2 atm pressure?

• A. zero cal
• B. 540 cal
• C. 517 cal
• D. None of above

Answer 1

The correct option is C 517 cal

The free energy change $\left(\Delta G\right)$ when 1.0 mole of water at ${100}^{\circ }C$ and 1 atm pressure is converted into steam at ${100}^{\circ }C$ and 1 atm pressure is 0 cal as the system is at equilibrium.

The free energy change $\left(\Delta G\right)$ when pressure of steam is increased from 1 atm to 2 atm is

$\Delta G=2.303RTlog\left(\frac{P_2}{P_1}\right)$

$\Delta G=2.303\times 2\times 373\times log\left(\frac{2}{1}\right)=517cal$

The free energy change $\left(\Delta G\right)$ when 1.0 mole of steam at ${100}^{\circ }C$ and 1 atm pressure is converted into steam at ${100}^{\circ }C$ and 1 atm pressure is $0+517=517$ cal.

Hence, the correct option is $C$