Chapter 18

Question 1

How is speed of reaction determined?

Answer 1

Either by measuring, per unit time, :
- volume of gas produced
OR
- change in mass of a reaction mixture

Question 2

For a graph of change in mass or volume of the reactants (or products), how can you tell the speed of reaction?

Answer 2

By looking at the gradient. The larger the gradient, the higher the speed of reaction.

Question 3

How does concentration of reactant influence speed of reaction?

Answer 3

Increasing the concentration of a reactant increases the speed of reaction.

Question 4

How does pressure of a gaseous reactant affect speed of reaction?

Answer 4

Increasing pressure of a gaseous reactant increases speed of reaction.

Question 5

How does surface area of a solid reactant (or particle size) influence speed of reaction?

Answer 5

Increasing the surface area of a solid reactant (i.e. decreasing the particle size) increases the speed of reaction.

Question 6

How does temperature affect speed of reaction?

Answer 6

Increasing temperature increases speed of reaction.

Question 7

What is a catalyst?

Answer 7

A substance which increases the speed of a chemical reaction and remains chemically unchanged at the end of the reaction.

Question 8

How do catalysts increase speed of reaction?

Answer 8

Catalysts do so by providing an alternative pathway for the reaction to proceed. The catalysed reaction has a lower activation energy than the reaction without the catalyst.

Question 9

What are enzymes?

Answer 9

Substances that catalyse the chemical reactions in plants and animals. They are biological catalysts.