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01/10/2020 8:40 pm
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The vapour pressure of pure benzene at a certain temperature is 0.850 bar. A non-volatile, nonelectrolyte solid weighing 0.5 g is added to 39.0 g of benzene (molar mass 78 g/mol). The vapour pressure of the solution then is 0.845 bar. What is the molecular mass of the solid substance?
(a) 58
(b) 180
(c) 170
(d) 145
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01/10/2020 8:44 pm
(c) 170
Explanation:
p°benzene = 0.850 bar; Wbenzene = 39.0g
M.W. = 78 g/mol
p°solution = 0.845 bar; w = 0.5 g
Let n be the no. of moles of non volatile solid; w and m be the weight of solid and molecular mass respectively.