2.2- Rates of Reaction

Question 1

(a)

Factors affecting rates of reaction

Answer 1

• concentration of a solution (pressure of a gas)
• surface area of a solid
• temperature
• catalyst
• light (in some reactions)

Question 2

(a)

Collision theory

Answer 2

Collision theory explains reaction rates by considering how often and effectively particles collide. For a reaction to occur, molecules must collide with the correct orientation and enough energy to overcome the activation energy. The rate of reaction depends on the frequency of these effective collisions—any factor that increases them will speed up the reaction.

Question 3

(b)

how to calculate rates from experimental data and how to establish the
relationship between reactant concentrations and rate

Question 4

(c)

Exothermic energy profile

Answer 4

In an exothermic reaction, the products have less energy than the reactants, and the excess energy is released as heat, making ΔH negative. However, energy (activation energy, Ea) is still needed to break bonds and start the reaction.

Question 5

(c)

Endothermic energy profile

Answer 5

In an endothermic reaction, the products have more energy than the reactants, so heat is absorbed from the surroundings, making ΔH positive.

Question 6

(c)

Activation energy

Answer 6

The minimum amount of energy required for a reaction to take place between two particles.