1.

The amount of solute (molar mass "60 g mol"^(-1)) that must be added to 180 g of water so that the vapour pressure of water is lowered by 10% is

Answer»

<P>30 g
60 g
120 g
12 g

Solution :If `p^(@)="100 mm, "p_(s)=100-10="90 mm"`
`(p^(@)-p_(s))/(p^(@))=(w_(2)//M_(2))/(w_(1)//M_(1))=(w_(2))/(M_(2))xx(M_(1))/(w_(1))`
`(100-90)/(100)=(w_(2))/(60)xx(18)/(180)`
`"or"w_(2)=(10)/(100)xx60xx10=60g.`


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