Question

The vapour pressure of a 5% aqueous solution of non-volatile organic substance at 373 k is 745 mm. calculated the molecular mass of the solute

Options

• 90 g ml^–1

• 120 g ml^–1

• 47 g ml^–1

• 12 g ml^–1

Answer 1

47 g ml^–1 

Explanation:

According to R adult law

= `(PÅ - Ps)/(Ps) = (nB)/(nA) = (WB)/(MB) xx (MA)/(WA)`

`((760  mm - 745  mm))/(745  mm) = (5  g xx (18  g  mol^-1))/(MB xx (25  g))`

`15/754 = (5  g xx 18  g  mol^-1)/(MB xx 95)`

MB = `(5  g xx 18  g  mol^-1)/(9  Jg  xx 15)` = 47 g ml^–1