Notes On Importance And Applications - CBSE Class 12 Chemistry
Coordination compounds play a vital role in analytical chemistry, metallurgy, biological systems, industry and medicine. (I) Applications of coordination compounds in analytical chemistry: Coordination compounds have many applications in qualitative as well as quantitative chemical analysis. (a) In the qualitative methods of analysis, complex formation is of immense importance in the identification and separation of most inorganic ions. Ex: When copper sulphate solution is mixed with aqueous ammonia, a deep blue complex soluble in water is formed. This reaction is used to detect cupric ions in the salt. (b) In numerous reactions of quantitative analysis the complexes are formed. Ex: Formation of a scarlet red complex with dimethyl glyoxime is the basis for the detection and estimation of Ni+2 ions. (c) The hardness of water is estimated by titration with the sodium salt of EDTA. During titration, the calcium and magnesium ions in hard water form the stable complexes, Calcium EDTA and Magnesium EDTA. These ions can be selectively estimated due to the difference in the stability constants of calcium and magnesium EDTA complexes. (II)  Application of complexes in metallurgy: (a) Noble metals like silver and gold are extracted from their ore by the formation of cyanide complexes - dicyanoargentite(I) and dicyanoaurate (I). (b) Metals can be purified by the formation and subsequent decomposition of their coordination compounds. Ex: Nickel can be purified by its reaction with carbon monoxide to form the volatile complex, tetracarbonyl Nickel (0), which is decomposed thermally to yield pure Nickel. (III) Naturally occurring coordination compounds are vital to living organisms. Metal complexes play a variety of important roles in biological systems. (a) Ex: Chlorophyll, pigment responsible for photosynthesis is a coordination compound of Magnesium. (b) Haemoglobin, red pigment of blood that acts as the Oxygen carrier is a coordination compound of iron. (c) Many enzymes that regulate biological processes are metal complexes. Ex: Carboxy peptidase, a hydrolytic enzyme important in digestion, contains a zinc ion coordinated to several amino acid residues of the protein. (IV) Applications of coordination compounds as catalysts in industrial processes: (a) In the hydrogenation of alkenes used a complex metal catalyst- tris triphenyl phosphine rhodium (I) chloride which is also known as Wilkinson's catalyst. (b) Ziegler-Natta catalyst, which is a combination of titanium tetrachloride and tri ethyl aluminium is used in the polymerisation of ethene. (V) Coordination compounds are also used in medicine: (a) British anti-lewisite (or) BAL is used as an antidote for arsenic poisoning. (b) EDTA is used to treat lead poisoning.

#### Summary

Coordination compounds play a vital role in analytical chemistry, metallurgy, biological systems, industry and medicine. (I) Applications of coordination compounds in analytical chemistry: Coordination compounds have many applications in qualitative as well as quantitative chemical analysis. (a) In the qualitative methods of analysis, complex formation is of immense importance in the identification and separation of most inorganic ions. Ex: When copper sulphate solution is mixed with aqueous ammonia, a deep blue complex soluble in water is formed. This reaction is used to detect cupric ions in the salt. (b) In numerous reactions of quantitative analysis the complexes are formed. Ex: Formation of a scarlet red complex with dimethyl glyoxime is the basis for the detection and estimation of Ni+2 ions. (c) The hardness of water is estimated by titration with the sodium salt of EDTA. During titration, the calcium and magnesium ions in hard water form the stable complexes, Calcium EDTA and Magnesium EDTA. These ions can be selectively estimated due to the difference in the stability constants of calcium and magnesium EDTA complexes. (II)  Application of complexes in metallurgy: (a) Noble metals like silver and gold are extracted from their ore by the formation of cyanide complexes - dicyanoargentite(I) and dicyanoaurate (I). (b) Metals can be purified by the formation and subsequent decomposition of their coordination compounds. Ex: Nickel can be purified by its reaction with carbon monoxide to form the volatile complex, tetracarbonyl Nickel (0), which is decomposed thermally to yield pure Nickel. (III) Naturally occurring coordination compounds are vital to living organisms. Metal complexes play a variety of important roles in biological systems. (a) Ex: Chlorophyll, pigment responsible for photosynthesis is a coordination compound of Magnesium. (b) Haemoglobin, red pigment of blood that acts as the Oxygen carrier is a coordination compound of iron. (c) Many enzymes that regulate biological processes are metal complexes. Ex: Carboxy peptidase, a hydrolytic enzyme important in digestion, contains a zinc ion coordinated to several amino acid residues of the protein. (IV) Applications of coordination compounds as catalysts in industrial processes: (a) In the hydrogenation of alkenes used a complex metal catalyst- tris triphenyl phosphine rhodium (I) chloride which is also known as Wilkinson's catalyst. (b) Ziegler-Natta catalyst, which is a combination of titanium tetrachloride and tri ethyl aluminium is used in the polymerisation of ethene. (V) Coordination compounds are also used in medicine: (a) British anti-lewisite (or) BAL is used as an antidote for arsenic poisoning. (b) EDTA is used to treat lead poisoning.

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