Which of the following is TRUE of a catalyst? I. it alters the activation energy of a reaction II. it is effective in a reaction but cannot initiate…

A catalyst is a substance that speeds up a chemical reaction without being used up itself. It works by providing an alternative reaction pathway that has a lower activation energy. This means less energy is needed for the reacting particles to successfully collide and form products.

A catalyst can only speed up a reaction that is already possible. It cannot start or initiate a reaction on its own. It simply makes a feasible reaction happen faster by lowering the energy barrier.

A catalyst does not change the position of equilibrium in a reversible reaction. It speeds up both the forward and backward reactions equally, so the same equilibrium mixture is reached, just faster. This means it does not affect the overall yield of product at equilibrium.

A catalyst also does not change the overall enthalpy change (energy change) of a reaction. The total energy difference between reactants and products stays the same. It only changes the route the reaction takes, not the start or end points.

So statements I (alters activation energy) and II (effective but cannot initiate) are correct. Statements III (affects equilibrium) and IV (affects overall reaction) are wrong.