P and Q are isomers of dicarboxylic acid C₄H₄O₄. Both decolorise Br₂/H₂O. On heating, P forms the cyclic anhydride. Upon treatment with dilute alkaline KMnO₄, P as well as Q could produce one or more than one from S, T and U.

In the following reaction sequences V and W are, respectively,

A fixed mass m of a gas is subjected to transformation of states from K to L to M to N and back to K as shown in the figure.

The succeeding operations that enable this transformation of states are

A fixed mass m of a gas is subjected to transformation of states from K to L to M to N and back to K as shown in the figure.

The pair of isochoric processes among the transformation of states is

The reaction of Cl₂ gas with cold-dilute and hot-concentrated NaOH in water give sodium salts of two (different) oxoacids of chlorine, P and Q, respectively. The Cl₂ gas reacts with SO₂ gas, in presence of charcoal, to give a product R. R reacts with white phosphorus to give a compound S. On hydrolysis, S gives an oxoacid of phosphorus, T.