Thermodynamic Parameters and Stability Constants of Chromium (III) Complexes of Carbohydrazone and Thiocarbohydrazone

Stability constants of two ligands, derived from 4-methyl-7-hydroxy-8-acetyl coumarin with carbohydrazide and thiocarbohydrazide and formation constants of their Chromium (III) complexes have been determined pH metrically at two different temperatures using Calvin and Melchior's extension of Bjerrum's method. The stability constants decrease with the increase in temperature. The thermodynamic parameters ΔG, ΔH and ΔS have been calculated. The values of ΔG and ΔH have been found to be negative and ΔS values are positive for both complexes.