Rates Of Reaction

Question 1

What is a catalyst?

Answer 1

A substance that speeds up chemical reactions without being used up or chemically changed

Question 2

Why use a catalyst? (3)

Answer 2

• reactions take place at lower temperatures and pressures
• reduces energy usage
• saves time and money

Question 3

What needs to happen to atoms for a reaction to happen?

Answer 3

Groups of atoms need to collide

Question 4

What is the activation energy?

Answer 4

The minimum energy needed for a reaction to happen

Question 5

How can the rate of reaction be increased? (4)

Answer 5

INCREASE:

1. Temperature
2. Concentration
3. Pressure
4. Surface area

Question 6

How does concentration increase the rate of reaction?

Answer 6

More particles increases the number of reactant particles in the same volume

More collisions per second

Question 7

How does surface area increase the rate of reaction?

Answer 7

When in a large lump (small sa) only the outer particles are exposed

When in small pieces (large sa) every particle is exposed and can react

Question 8

How does temperature increase the rate of reaction? (2)

Answer 8

More energy means more successful collisions

The speed increases, meaning more collisions per second

Question 9

What is the rate?

Answer 9

The speed at which reactants are turned into products

Question 10

What are reactants?

Answer 10

A substance that takes part in a change during a reaction

Question 11

What is a precipitation reaction?

Answer 11

When you mix two see through solutions to produce a precipitate, which clouds the solution

Question 12

How do you know if a reaction is a precipitation reaction?

Answer 12

It is a very fast reaction

Question 13

What is an example of a very slow reaction?

Answer 13

The rusting of iron

Question 14

What is used to measure gas volumes accurately?

Answer 14

A gas syringe

Question 15

How do catalysts work?

Answer 15

They provide an alternative reaction route which requires less activation energy

Question 16

What is a reaction profile?

Answer 16

A graph that shows the energy changes with and without a catalyst in an exothermique reaction

Question 17

What is an exothermic reaction?

Answer 17

The making of bonds

Question 18

What is an endothermic reaction?

Answer 18

The breaking of bonds

Question 19

What is the method for showing how surface area affects rate which uses a gas syringe?

Answer 19

1. Add measured amount of marble chips
2. Add measured amount of hydrochloric acid
3. Put in rubber bung with glass tube
4. Connect gas syringe

Question 20

What is the method for showing how surface area affects rate which uses cotton wool?

Answer 20

1. Add measured amount of marble chips
2. Add measured amount of hydrochloric acid
3. Put cotton wool in top to allow gas out
4. Measure mass every 20 seconds

Question 21

What are 2 sources of error in the precipitation reaction?

Answer 21

Not easy to see when cross disappears

The temperature changes as the reaction proceeds

Question 21

How can you reduce the errors of a precipitation reaction?

Answer 21

Conduct the reaction in the water so the temperature doesn’t change

Use a colorimeter

Question 22

What is dynamic equilibrium?

Answer 22

When the forwards and backwards reactions in a reversible chemical reaction which occur at the same rate