The mass of non-volatile solute of molar mass 40 g/mol that should be dissolved in 114 g of octane to lower its vapour pressure by 20% is (KCET 2012)

o Given,p 100,p 100 20 80 , 1 2 M 40g mol 1 8 18 2 1 M octane C H 12 8 18 114 w ?,w octane 114g x o 2 1 o 2 1 2 2 w M p p , M w p w 100 80 114 100 40 114 w 20 or 8g 100 40 x x