Question

Explain the factors influencing the rate of a reaction.

Answer 1

Important factors that affect the rate of a reaction are:

1. Nature of the reactants
2. The concentration of the reactants
3. Temperature
4. Catalyst
5. Pressure
6. The surface area of the reactants

1. Nature of the reactants: The reaction of sodium with hydrochloric acid is faster than that with acetic acid because Hydrochloric acid is a stronger acid than acetic acid and thus more reactive. So, the nature of the reactants influences the reaction rate.

2Na_(s) + 2HCl_(aq) → 2NaCl_(aq) + H_2(g) (fast)

2Na_(s) + 2CH₃COOH_(aq) → 2CH₃COONa_(aq) + H_2(g) (slow)

2. Concentration of the reactants: Changing the amount of the reactants also increases the reaction rate. The more the concentration, the more particles per volume exist in it, and hence the faster the reaction. Granulated zinc reacts faster with 2M hydrochloric acid than 1M hydrochloric acid.

3. Temperature: Most of the reactions go faster at higher temperatures. Because adding heat to the reactants provides energy to break more bonds and thus speed up the reaction. Calcium carbonate reacts slowly with hydrochloric acid at room temperature. When the reaction mixture is heated the reaction rate increases.

4. Pressure: If the reactants are gases, increasing their pressure increases the reaction rate. This is because on increasing the pressure the reacting particles come closer and collide frequently.

5. Catalyst: A catalyst is a substance that increases the reaction rate without being consumed in the reaction. In certain reactions, adding a substance as a catalyst speeds up the reaction. For example, on heating potassium chlorate, it decomposes into potassium chloride and oxygen gas, but at a slower rate. If manganese dioxide is added, it increases the reaction rate.

6. Surface area of the reactants: Powdered calcium carbonate reacts more readily with hydrochloric acid than marble chips. Because powdering of the reactants increases the surface area and more energy is available on collision of the reactant particles. Thus, the reaction rate is increased.