For an elementary chemical reaction,



the expression for $${{d\left[ A \right]} \over {dt}}$$ is

An aromatic compound 'A' having molecular formula C₇H₆O₂ on treating with aqueous ammonia and heating forms compound 'B'. The compound 'B' on reaction with molecular bromine and potassium hydroxide provides compound 'C' having molecular formula C₆H₇N.. The structure of 'A' is

The pair that contains two P – H bonds in each of the oxoacids is

A reaction of cobalt (III) chloride and ethylenediamine in a 1 : 2 mole ratio generates two isomeric products A (violet coloured) and B (green coloured). A can show optical activity, but B is optically inactive. What type of isomers does A and B represcent?