The property of a chemical reaction that is affected by the presence of a catalyst is

The property of a chemical reaction that is affected by the presence of a catalyst is the activation energy. Activation energy is the energy required for a chemical reaction to occur. Catalysts are substances that can speed up a chemical reaction by lowering the activation energy required for the reaction to happen. This means that the same chemical reaction that would otherwise require a lot of energy to start, can happen more easily and with less energy input in the presence of a catalyst. Imagine trying to push a heavy object up a hill - it takes a lot of effort and energy to get it started. But if there's a ramp, it becomes much easier to push the object up the hill, and less energy is required. In the same way, a catalyst acts like a ramp for a chemical reaction, making it easier for the reaction to occur with less energy input.