The density of `10% ` by mass of KCI solution in water is ` 1 . 0 6 g mL^(-1)` . Calculate molarity and molality of the solution

Answer

1.42 M, 1.49

Explanation

Mass of solution = 100 g (say)
`:.` Mass of KCI = 10 g
Volume of solution `= ("Mass")/( "Density")`
`= (100 g)/(1 . 0 6 g mL^(-1)) = 94 . 34 ` mL
= 0 . 0 94 34 L
Molar mass of KCI = 39 + 35 . 5
`= 74 . 5 g mol^(-1)`
No, of moles of KCI
`n_(B) = (10 g)/( 74 . 5 g mol^(-1)) = 0 . 13423 ` mol
Molarity
`= ("No. of moles of KCI")/("Vol . of solution ") = (0 . 13423 mol)/( 0 . 09434 L)` Mass of solvent
= 100 - 10 = 90 g
= 0 .090 kg
Molality `= ("No. of mole of KCI")/("Mass. of solution ") = (0 . 13423 mol)/( 0 . 090 kg) `
`= 1 . 4914 mol kg^(-1) = 1 . 49 m`