Q.The addition of a catalyst during a chemical reaction alters which of the following quantities? (NEET)

A catalyst alters a reaction's rate WITHOUT itself undergoing any permanent chemical change -- it may take part in an intermediate mechanistic step but is fully regenerated by the reaction's end. Mechanistically, a catalyst opens an ALTERNATIVE pathway with a LOWER activation energy $E_a$; since the fraction of sufficiently energetic collisions is $f=e^{-E_a/RT}$, even a modest cut in $E_a$ lets far more molecules cross the barrier per second at the same temperature, raising the observed rate. Crucially, a catalyst changes only the PATHWAY and the RATE -- never the reaction's thermodynamics (same reactants, same products, same overall energy change); only the height of the intervening energy hill differs. …