Chapter: Solutions· Chemistry

The normal boiling point of ethyl acetate is 77.06 ºC. A solution of 50 g of non-volatile solute in 150 g ethyl acetate boils at 82.60 ºC. Calculate molar mass of solute. [ Kb = 2.77ºC kg mol–1 ]

Q.3 The normal boiling point of ethyl acetate is 77.06 ºC. A solution of 50 g of non-volatile solute in 150 g ethyl acetate boils at 82.60 ºC. Calculate molar mass of solute. [ K_b = 2.77ºC kg mol^–1 ]

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Answer: Molar mass of solute ≈ 166.7 g mol⁻¹

Given: \(T_b^0 = 77.06\) ºC, \(T_b = 82.60\) ºC, \(W_2 = 50\) g, \(W_1 = 150\) g, \(K_b = 2.77\) ºC kg mol⁻¹.

\(\Delta T_b = T_b - T_b^0 = 82.60 - 77.06 = 5.54\) ºC (= 5.54 K)

\(M_2 = \dfrac{1000\,K_b\,W_2}{\Delta T_b\,W_1} = \dfrac{1000 \times 2.77 \times 50}{5.54 \times 150} = \dfrac{138500}{831} = 166.67\) g mol⁻¹

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The normal boiling point of ethyl acetate is 77.06 ºC. A solution of 50 g of non-volatile solute in 150 g ethyl acetate boils at 82.60 ºC. Calculate molar mass of solute. [ Kb = 2.77ºC kg mol–1 ]

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