Question

Molar heat capacity of water (liquid) in equilibrium with water vapour at constant pressure is:

• A. Zero
• B. $\infty$
• C. $75.48$ J mol ${}^{-1}$ K${}^{-1}$
• D. $40.45$ J mol ${}^{-1}$ K${}^{-1}$

Answer 1

The correct option is C $75.48$ J mol ${}^{-1}$ K${}^{-1}$

Water in equilibrium with ice has a steady temperature of zero degree celcius

Water in liquid state, has a specific heat of exactly 1 calorie per gram

Molar mass of water is $15.999+2.016=18.015$ grams per mole

Therefore, the molar heat capacity of water at zero degree celcius

$=18.015\times 1calorie/mol/k$

$=18.015\times 1\times 4.184J/mol/k$

$=75.48J/mol/k$