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The Vapour pressure of water at 293 K is 0.0231 bar and the vapour pressure of the solution of 108.24 g of a compound in 1000 g of water at the same temperature. Calculate the molar mass of the solute. |
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Answer» Vapour pressure of solvent pA0 = 0.0231 bar Vapour pressure of solution pA0 = 0.0228 bar Lowering in vapour pressure pA0 - pA = 0.0231 - 0.0228 = 0.0003 bar Weight of solvent WA = 1000 g Weight of solute WB = 108.24 g Molar mass of the solvent MA = 18 Molar mass of the solute MB = ? We know that pA˚ - pA / p0A = WB MA/WA MB MB = WB MA PA˚/ WA (PA˚ - PA) = 108.24 X 0.0231 X 18/ 0.0003 X 1000 = 150 g mol-1 |
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