Estimate K_f of water from T_f = 273 K, molar mass 18 g mol^-1, Delta H_fus = 6000 J mol^-1 and R = 8.314 J mol^-1 K^-1, using K_f = (M R T_f^2)/(1000 Delta H_fus) with M in g mol^-1. Give the answer in K kg mol^-1 to two decimal places.

JEE Main levelNumerical answerDifficulty 2 of 3so065

Estimate $K_{f}$ of water from $T_{f} = 273 K$ , molar mass $18 g mo l^{- 1}$ , $Δ H_{f u s} = 6000 J mo l^{- 1}$ and $R = 8.314 J mo l^{- 1} K^{- 1}$ , using $K_{f} = \frac{MR T _{f}^{2}}{1000 Δ H _{f u s}}$ with $M$ in $g mo l^{- 1}$ . Give the answer in $K kg mo l^{- 1}$ to two decimal places.

Numerical answer type, answer in K kg/mol, tolerance 0.01.

K_{f} = \frac{18 \times 8.314 \times 27 3 ^{2}}{1000 \times 6000} = 1.859 K kg mo l^{- 1}