The rate and extent of chemical change

Question 1

If a reversible reaction is endothermic in forward direction, what will it be in the reverse direction?

Answer 1

Exothermic

Question 2

Which reaction shows the fastest rate of reaction? A, B or C?

Answer 2

A

Question 3

For a reversible reaction at equilibrium, what effect will decreasing temperature have on the exothermic reaction

Answer 3

The amount of product increases

Question 4

What effect will increasing the concentration of a reactant have on a reversible reaction?

Answer 4

• More products will be formed
• Until equilibrium is reached again

Question 5

What theory states that chemical reactions only occur when reacting particles collide with enough energy?

Answer 5

Collision Theory

Question 6

Calculate the mean rate of reaction for a reaction producing 50 cm³ of gas in 5 s (Give the correct units).

Answer 6

50 cm³ / 5 s = 10 cm³/s

Question 7

What is a catalyst?

Answer 7

A substance that increases the rate of a reaction without being used up in the reaction by providing an alternative pathway with a lower activation energy.

Question 8

What is Le Chatelier’s Principle?

Answer 8

The idea that if you change the conditions(such as temperature and pressure) of a reversible reaction at equilibrium, the system will try to counteract the change.

Question 9

Calculate the mean rate of reaction for a reaction where 5 g of calcium carbonate completely reacts in 10 s (Give the correct units).

Answer 9

5 g / 10 s = 0.5 g/s

Question 10

For a reversible reaction at equilibrium, what effect will increasing temperature have on the endothermic reaction

Answer 10

The amount of product increases

Question 11

Explain how pressure affects the rate of reaction.

Answer 11

Increasing the pressure……increases the frequency of collisions……and so increases the rate of reaction.

Question 12

Explain how concentration affects the rate of reaction.

Answer 12

Increasing the concentration……increases the frequency of collisions……and so increases the rate of reaction.

Question 13

What is the name for the straight line drawn next to the curve at the point indicated by the arrow?

Answer 13

Tangent

Question 14

How would you add a line to show the effect of a catalyst on the reaction profile below?

Answer 14

Question 15

What two equations can be used to measure the rate of a reaction?

Answer 15

Question 16

For a gaseous reaction at equilibrium, what would be the effect of increasing pressure

Answer 16

Equilibrium position will shift towards the side with the smaller number of molecules

Question 17

What does ‘equilibrium’ mean?

Answer 17

In a reversible reaction, the forward and reverse reactions occur at exactly the same rate.

Question 18

For a reversible reaction at equilibrium, what effect will increasing temperature have on the exothermic reaction

Answer 18

The amount of product decreases

Question 19

Explain how temperature affects the rate of reaction.

Answer 19

Increasing temperature……Increases the frequency of collisions……The collisions are more energetic.

Question 20

How does a catalyst work?

Answer 20

Catalysts increase the rate of reaction……by providing an alternative pathway for the reaction……with a lower activation energy.

Question 21

What is the name for the minimum amount of energy needed for a reaction to happen?

Answer 21

Activation Energy

Question 22

List the 5 things that can affect the rate of a reaction.

Answer 22

1. Concentration (of solutions)
2. Pressure (of gases)
3. Surface area (of solids)
4. Temperature
5. Catalysts

Question 23

For a gaseous reaction at equilibrium, what would be the effect of decreasing pressure

Answer 23

Equilibrium position will shift towards the side with the larger number of molecules

Question 24

Calculate the rate of reaction when 2 moles of magnesium oxide reacts in 4 seconds.

Answer 24

2 moles / 4 s = 0.5 mol/s

Question 25

How would you calculate the rate of the reaction at the point indicated by the arrow?

Answer 25

• Draw a tangent at that point
• Calculate the gradient of the tangent

Question 26

Explain how surface area affects the rate of reaction.

Answer 26

Increasing the surface area ……increases the frequency of collisions……and so increases the rate of reaction.

Question 27

For a reversible reaction at equilibrium, what effect will decreasing temperature have on the endothermic reaction

Answer 27

The amount of product decreases

Question 28

What is the symbol for a reversible reaction?

Answer 28