18) C

A – a catalyst would increase the rate of reaction rather than decrease it. A is wrong

B – This is not true as gases have larger surface area than solid and we know that the higher the surface area, the higher the rate of reaction. B is wrong

C – this is true because activation energy is the energy required to start a reaction. If the activation energy is high, there will be lesser successful collisions. This means that there would be a slower rate of reaction. C is correct

D – Increasing the temperature means that the particles would have more energy and there would more successful collision. This would result in a higher rate of reaction. D is wrong.

E – This is not necessarily true as all products and reactants are gas, meaning that there may not be a change in volume