Name: Nomenclature of Coordination Compounds - I
Uploaded: 2019-07-19
Duration: 7 min 4 s
Description: All the chemical compounds are assigned a name, which is done according to a specific rule. How are coordination compounds named? Let’s watch the video to fi...

Question

What do you understand by the stability constant,

K_{s}

of a complex. Knowing that the value of

K_{s}

for

{[Cu {({NH}_{3})}_{4}]}^{2 +}

is

4.5 \times 10^{11}

and for

{[Cu {(CN)}_{4}]}^{2 -}

is

2.0 \times 10^{27}

. Suggest (a) which complex species will furnish less

{Cu}^{2 +}

ions in the solution. (b) which out of

({NH}_{3})

and

({CN}^{-})

is a stronger base?

Accepted Answer

A stability constant which is also called formation constant is an equilibrium constant for the formation of a coordination complex in a solution. It is a measure of the strength of the interaction between the reagents that come together to form the complex in a chemical reaction. For the reaction: $M + 3 L ⇌ {ML}_{3}$ ,

Stability constant $(K_{s}) = \frac{[{ML}_{3}]}{[M] {[L]}^{3}}$

(a) Stability constant for ${[Cu {({NH}_{3})}_{4}]}^{2 +}$ is given as:

$K_{s} = \frac{{[Cu {({NH}_{3})}_{4}]}^{2 +}}{[{Cu}^{2 +} (aq)] {[{NH}_{3} (aq)]}^{4}} = 4.5 \times 10^{11}$

Stability constant for ${[Cu {(CN)}_{4}]}^{2 -}$ is given as:

$K_{s} = \frac{{[Cu {(CN)}_{4}]}^{2 -}}{[{Cu}^{2 +} (aq)] {[{CN}^{-} (aq)]}^{4}} = 2.0 \times 10^{27}$

Clearly, the concentration of ${Cu}^{2 +}$ furnished by $2.0 \times 10^{27}$ is less compared to that furnished by ${[Cu {({NH}_{3})}_{4}]}^{2 +}$ complex ion.

(b). As ${CN}^{-}$ ligand formed more stable coordination complex with ${Cu}^{2 +}$ compared to ${NH}_{3}$ ligand, thus, ${CN}^{-}$ ligand is a stronger base than ${NH}_{3}$ .

Important Questions on Coordination Compounds

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What do you understand by the stability constant, Ks of a complex. Knowing that the value of Ks for CuNH342+ is 4.5×1011 and for CuCN42- is 2.0×1027. Suggest (a) which complex species will furnish less Cu2+ ions in the solution. (b) which out of NH3 and CN- is a stronger base?

Important Questions on Coordination Compounds

Learn and Prepare for any exam you want !