From the stability constant (hypothetical values) given below, predict which is the strongest ligand?
A
C u 2 + + 4 N H 3 ⇋ [ C u ( N H 3 ) 4 ] 2 + ; ( K = 4.5 × 10 11 ) \mathrm{C}{\mathrm{u}^{2 + }} + 4\mathrm{N}{\mathrm{H}_3}\leftrightharpoons{\left[ {\mathrm{Cu}{{\left( {\mathrm{N}{\mathrm{H}_3}} \right)}_4}} \right]^{2 + }}\mathrm{\;\;};\left( {K = 4.5 \times {{10}^{11}}} \right) C u 2 + + 4 N H 3 ⇋ [ Cu ( N H 3 ) 4 ] 2 + ; ( K = 4.5 × 10 11 )
B
C u 2 + 4 C N ⇋ [ C u ( C N ) 4 ] 2 − ; ( K = 2.0 × 10 27 ) \mathrm{C}{\mathrm{u}^2} + 4\mathrm{CN}\leftrightharpoons{\left[ {\mathrm{Cu}{{\left( {\mathrm{CN}} \right)}_4}} \right]^{2 - }}\mathrm{\;};\left( {K = 2.0 \times {{10}^{27}}} \right) C u 2 + 4 CN ⇋ [ Cu ( CN ) 4 ] 2 − ; ( K = 2.0 × 10 27 )
C
C u 2 + + 2 e n ⇋ [ C u ( e n ) 2 ] 2 + ; ( K = 3.0 × 10 15 ) \mathrm{C}{\mathrm{u}^{2 + }} + 2\mathrm{en}\leftrightharpoons{\left[ {\mathrm{Cu}{{\left( {\mathrm{en}} \right)}_2}} \right]^{2 + }}\mathrm{\;};\mathrm{\;\;}\left( {K = 3.0 \times {{10}^{15}}} \right) C u 2 + + 2 en ⇋ [ Cu ( en ) 2 ] 2 + ; ( K = 3.0 × 10 15 )
D
C u 2 + + 4 H 2 O ⇋ [ C u ( H 2 O ) 4 ] 2 + ; ( K = 9.5 × 10 8 ) \mathrm{C}{\mathrm{u}^{2 + }} + 4{\mathrm{H}_2}\mathrm{O}\leftrightharpoons{\left[ {\mathrm{Cu}{{\left( {{\mathrm{H}_2}\mathrm{O}} \right)}_4}} \right]^{2 + }}\mathrm{\;};\left( {K = 9.5 \times {{10}^8}} \right) C u 2 + + 4 H 2 O ⇋ [ Cu ( H 2 O ) 4 ] 2 + ; ( K = 9.5 × 10 8 )
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Correct option: B
C u 2 + 4 C N ⇋ [ C u ( C N ) 4 ] 2 − ; ( K = 2.0 × 10 27 ) \mathrm{C}{\mathrm{u}^2} + 4\mathrm{CN}\leftrightharpoons{\left[ {\mathrm{Cu}{{\left( {\mathrm{CN}} \right)}_4}} \right]^{2 - }}\mathrm{\;};\left( {K = 2.0 \times {{10}^{27}}} \right) C u 2 + 4 CN ⇋ [ Cu ( CN ) 4 ] 2 − ; ( K = 2.0 × 10 27 ) Option B (
C u 2 + 4 C N ⇋ [ C u ( C N ) 4 ] 2 − ; ( K = 2.0 × 10 27 ) \mathrm{C}{\mathrm{u}^2} + 4\mathrm{CN}\leftrightharpoons{\left[ {\mathrm{Cu}{{\left( {\mathrm{CN}} \right)}_4}} \right]^{2 - }}\mathrm{\;};\left( {K = 2.0 \times {{10}^{27}}} \right) C u 2 + 4 CN ⇋ [ Cu ( CN ) 4 ] 2 − ; ( K = 2.0 × 10 27 ) ) is correct because the stability constant (K) is highest for this reaction, indicating the strongest ligand.
