30.4 kJ of heat is required to melt one mole of sodium chloride and the entropy change at the melting point is $28.4 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$ at 1 atm. The melting point of sodium chloride is ______ K (Nearest Integer)

JEE Main · 2023 · 15 Apr 2023 · Shift 1 · Chemical Thermodynamics

30.4 kJ of heat is required to melt one mole of sodium chloride and the entropy change at the melting point is

28.4 J K^{- 1} mol^{- 1}

at 1 atm. The melting point of sodium chloride is ______ K
(Nearest Integer)

Answer: 1070

At the melting point solid and liquid are in equilibrium, so the Gibbs energy change is zero and

Δ H = T Δ S

. Rearranging gives

T = Δ H /Δ S

. With

Δ H = 30.4 kJ mo l^{- 1} = 30400 J mo l^{- 1}

and

Δ S = 28.4 J K^{- 1} mo l^{- 1}

T = 30400/28.4 = 1070.4 K

. The melting point of sodium chloride is 1070 K.

JEE Main · 2023 · 15 Apr 2023 · Shift 1 · Integer answer