The ionic strength of a solution containing 0.1 mole/kg of KCl and 0.2 mole/kg of CuSO4 is

Question

The ionic strength of a solution containing 0.1 mole/kg of KCl and 0.2 mole/kg of CuSO4 is (A) 0.3 (B) 0.6 (C) 0.9 (D) 0.2

Tardigrade Admin · Accepted Answer

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

I = \frac{1}{2} (m_{1} z_{1}^{2} + m_{2} z_{2}^{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

C l^{- 1}

ion,

m_{2} = 0.1 m, z_{2} = 1

For

C u^{2 +}

ion

m_{3} = 0.2 m, z_{3} = 2

For

S O_{4}^{2 -}

ion

m_{4} = 0.2 m, z_{4} = 2

∴

I = \frac{1}{2} [0.1 \times 1^{2} + 0.1 \times 1^{2} + 0.2 \times 2^{2} + 0.2 \times 2^{2}]

=

\frac{1}{2} [0.1 + 0.1 + 0.8 + 0.8]

=

\frac{18}{z}

= 0.9

Q. The ionic strength of a solution containing 0.1 mole/kg of KCl and 0.2 mole/kg of CuSO4​ is