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Question: In a solution total concentration of M<sup>3+</sup> is 2 × 10<sup>–3</sup>(M) and total concentratio...

In a solution total concentration of M3+ is 2 × 10–3(M) and total concentration of SCN– is 1.51 × 10–3(M) and free SCN– concentration = 1 × 10–5(M) What is the dissociation constant of the complex M (SCN)2+ ?

A

2 × 105

B

2 × 10–5

C

3.33 × 105

D

3.33 × 10–6

Answer

3.33 × 10–6

Explanation

Solution

M3+ + SCN– M(SCN)2+

50 × 10–5 10–5 150 × 10–5

Kform = 150×10−550×10−5×10−5\frac { 150 \times 10 ^ { - 5 } } { 50 \times 10 ^ { - 5 } \times 10 ^ { - 5 } }= 3 × 105

Kdisso = 13\frac { 1 } { 3 } × 10–5 = 103\frac { 10 } { 3 }× 10–6

= 3.33 × 10–6