GCSE Topic 7 - Rate of reaction

Question 1

What are the pieces of information that required to calculate the rate of reaction?

Answer 1

1. Time
2. Amount of reactant used or product produced

Question 2

List the factors that affect the rate of a reaction

Answer 2

• Catalyst
• Temperature
• Surface Area
• Concentration (solutions)
• Pressure (gases)

Question 3

Define a catalyst

Answer 3

A substance that speeds up the rate of a reaction by lowering the activation energy. It is not used up in the reaction.

Question 4

What are units for volume?

Answer 4

cm³

Question 5

Define an enzyme

Answer 5

A biological catalyst

Question 6

State some uses of enzymes

Answer 6

• Making ethanol in alcohol drinks
• Detergents
• Forensic analysis

Question 7

What group of elements are often catalysts?

Answer 7

Transition metals

Question 8

Desribe how a catalyst works

Answer 8

1. Reactant molecules adsorb onto the surface, forming temporary bonds with the catalyst.
2. Bonds within the molecules weaken and then break.
3. Atoms of the reactant molecules are rearranged to form the product molecules.
4. Product molecules desorb from the surface.

Question 9

What is the symbol equation for magnesium reacting with hydrochloric acid?

Answer 9

Mg _(s) + 2 HCl _(aq) ⇒ MgCl_{2 (aq)} + H_{2 (g)}

Question 10

What is the symbol equation for marble chips reacting with hydrochloric acid?

Answer 10

CaCO_{3 (s)} + 2 HCl _(aq) ⇒ CaCl_{2 (aq)} + H₂O _(l) + CO_{2 (g)}

Question 11

Explain why increasing temperature increases rate of reaction

Answer 11

• Reactant particles have more kintetic energy
• There is a greater proportion of reactant particles that have above the activation energy
• There are more frequent and successful collisions between reacant particles

Question 12

Explain why increasing concentration increases rate of reaction

Answer 12

• There are more reactant particles per unit volume
• There are more frequent and successful collisions

Question 13

Explain why increasing pressure increases rate of reaction

Answer 13

• There are more reactant gas particles per unit volume
• There are more frequent and successful collisions

Question 14

Explain why there is a greater of rate of reaction with powdered solids

Answer 14

• There is a greater surface area
• There are more exposed reactant particles
• There are more frequent anf successful colliisions

Question 15

Define an endothermic reaction

Answer 15

• A reaction where heat energy is taken in (specification)
• A reaction where there is an energy change from thermal to chemical
• There is a decrease in temperature

Question 16

Define an exothermic reaction

Answer 16

• A reaction where heat energy is given out (specification)
• A reaction where there is an energy change from chemical to thermal
• There is an increase in temperature

Question 17

What is the energy change with a salt dissolving in water?

Answer 17

Endothermic

Question 18

What is the energy change with a neutralisation reaction?

Answer 18

Exothermic

Question 19

What is the energy change with a displacement reaction?

Answer 19

Exothermic

Question 20

What is the energy change with a precipitation reaction?

Answer 20

Either exothermic or endothermic

Question 21

Is bond breaking endothermic or exothermic?

Answer 21

Endothermic

Question 22

Is bond making endothermic or exothermic?

Answer 22

Exothermic

Question 23

Explain in terms of bonds why a reaction is exothermic

Answer 23

More energy is released in making bonds than is used to break bonds

Question 24

Explain in terms of bonds why a reaction is endothermic

Answer 24

More energy is used to break bonds than is released in making bonds

Question 25

How is the energy change of reaction calculated using bond energies?

Answer 25

(Total bond energies of reactants) - (total bond energies of products)

Question 26

Define the term ‘activation energy’

Answer 26

The minimum energy needed to start a reaction

Question 27

What is the formula for calculating the rate of a reaction?

Answer 27

Rate = amount of product produced / time

Question 28

How can you tell from a graph when a reaction has stopped?

Answer 28

When the graph just starts to flatten

Question 29

Explain why the rate of reaction decreases as a reaction progresses

Answer 29

There are fewer reactant particles per unit volume

Question 30

Explain how the shape of a graph can be used to compare rates of reaction

Answer 30

The steeper the gradient, the higher the rate of reaction