The ionic strength of a solution containing `0.1"mole"//kg` of KCI and `0.2"mole"//kg` of `CuSO_(4)` is

Options

A. 0.3
B. 0.6
C. 0.9
D. 0.2

Answer

C

Explanation

Ionic strength is half of the sum of all the terms obtained by multiplying the molality of each ion by the square of its valency.
`1 = (1)/(2) (m_(1)z_(1)^(2) +m_(2)z_(2)^(2)+m_(3)z_(3)^(2)+m_(4)z_(4)^(2))`
Here for `K^(+)` ion,
`m_(1) = 0.1 m, z_(1) = 1`
For `CI^(-)` ion,
`m_(2) = 0.1m, z_(2) = 1`
For `Cu^(2+)` ion,
`m_(3) = 0.2m, z_(3) = 2`
For `SO_(4)^(2-)` ion
`m_(4) = 0.2 m, z_(4) = 2`
`:. 1 =(1)/(2)[0.1 xx 1^(2) +0.1 xx 1^(2) +0.2 xx 2^(2) +0.2 xx 2^(2)]`
`= (1)/(2) [0.1 +0.1 +0.8 +0.8]`
`= (1.8)/(2) = 0.9`