Question

increase or 7-9. Including activity coefficients, find [Hg3] in saturated Hg,Br2 in 0.001 00 M KBr.

Answer 1

First calculate ionic strength of KBr solution.

We have, = 1/2 Sum ( C _i Z _i² )

Where C _i is concentration of i th species and Z _i is its charge.

Charge on K is +1 and on Br is -1.

[K⁺] = [Br ^- ] = 0.00100 M

$\therefore$ The ionic strength is = 1/2 [ [K⁺] (+1) ² + [Br ^- ] (-1) ² ]

= 1/2 [ 0.00100 *1 + 0.00100 *1 ]

= 0.00100 M

For = 0.00100 M , Hg ₂²⁺ = 0.867 , Br ^- = 0.964

Consider dissociation of Hg₂Br₂ in KBr solution. Hg₂Br₂ (s) Hg ₂²⁺ (aq) + 2  Br ^- (aq)

For above reaction, Ksp =( [Hg ₂²⁺ ] Hg ₂²⁺ ) ( [Br ^- ] ²² Br ^- )

5.6 10 ^{- 23} = [Hg ₂²⁺ ] 0.867 (0.00100) ² ( 0.964) ²

5.6 10 ^{- 23} = [Hg ₂²⁺ ] 8.057 $\times$ 10 ^-07

[Hg ₂²⁺ ] = 5.6 $\times$ 10 ^{- 23} / 8.057 $\times$ 10 ^-07 = 7.0 $\times$ 10 ^-17 M

ANSWER : [Hg ₂²⁺ ] = 7.0 $\times$ 10 ^-17 M