Two liquids kX and Y on mixing form an ideal solution. The vepour pressure of the solution containing 3 moles X and 1 mole of Y is 550 mm Hg. But when 4 moles of X and I mole of Y and pure Y at this temperature?

Two liquids kX and Y on mixing form an ideal solution. The vepour pres

1.	Two liquids kX and Y on mixing form an ideal solution. The vepour pressure of the solution containing 3 moles X and 1 mole of Y is 550 mm Hg. But when 4 moles of X and I mole of Y and pure Y at this temperature?
Answer» SOLUTION :Let the vapourpressures of pure LIQUIDS X and Y be `P_(X)^(@) and P_(Y)^(@)` respecively Mole Fraction of `X=n_(x)/(n_(x)+n_(y))=3/(3+1)=3/4=0.75` Mole fraction of Y=`n_(Y)/(n_(x)+n_(y))=1/(3+1)=1/4=0.25` According to Raooult's Law , `P_(x)^(2)xx0.75+P_(Y)^(@)xx0.25=550 mm` Mole fraction of X=`n_(x)/(n_(x)+n_(y))=4/(4+1)=4/5=0.8` Mole fraction of Y=`n_(y)/(n_(x)+n_(y))=4/(4+1)=1/5=0.2` According to Roult's Law `P_(X)^(@)xx0.8+P_(Y)^(@)xx0.2=560 mm` Multiply EQUATION (i) by 4 and equation(ii) by 5 `3P_(X)^(@)+P_(Y)^(@)=550xx4=2200 mm` `4P_(X)^(@)+P_(Y)^(@)=560xx5=2800 mm` `-P_(X)^(@)=(2200-2800)-600mm` `P_(X)^(@)=600 mm` Substitute the value of `P_(X)^(@)` in equation `3xx(600mm)+P_(Y)^(@)=2200mm or P_(Y)^(@)=2200-1800=400mm`