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Molecular weight of substance

The boiling point of a solution of 0.11 gm of a substance in 15 gm of ether was found to be 0.1oC higher than that of the pure ether. The molecular weight of the substance will be (Kb = 2.16)       
(a) 148    (b) 158   (c) 168    (d) 178

Answer: (b) m = (Kb x w x 1000)/(ΔTb x W)
Kb = 2.16, w = 0.11, W = 15g, ΔTb = 0.1
m = (2.16 x 0.11 x 1000)/ (0.1 x 15) = 158.40 = 158

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