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QJEEM19Ch372f: JEE Main 2019 Chemistry - Class 11 JEEM19Ch372f Solution: What would be the molality of 20% (mass/ mass) aqueous solution …

What would be the molality of 20% (mass/ mass) aqueous solution of KI?
(molar mass of KI = 166 g mol^–1)

Step-by-Step Verified Solution

20% (mass/ mass) aqueous solution means,

100 g solution contains 20 g KI

\therefore

Mass of solvent = 100 – 20 = 80 g

So, 20 g of KI present in 80 g of solvent.

\therefore

{{20} \over {166}}

moles of KI present in 80 g of solvent.

We know,

Molality (m) =

{{no\,of\,moles\,of\,solute} \over {wt(in\,kg)\,of\,solvent}}

\therefore

m =

{{{{20} \over {166}}} \over {{{80} \over {1000}}}}

= 1.51