C2.4

Question 1

What do we mean by the rate of chemical reaction?

Answer 1

Tells us how fast reactants turn into products in your body.

Question 2

Why is understanding the rate of reactions so important in industry?

Answer 2

Have to make money by producing useful products.

Question 3

Name 2 ways we can find out the rate of reactions:

Answer 3

• how quickly the reactants are used up as they make products
• how wicket the products of the reaction are made

Question 4

What is the equation of rate of reactions?

Answer 4

=amount of reactant used or product formed/time

Question 5

What are the 4 main factors which affect the rate of chemical reactions?

Answer 5

• temperature
• surface area
• concentration of solution or pressure of gasses
• presence of a catalyst

Question 6

When do reactions take place?

Answer 6

Can only take place when the particles of reactants come together.

Question 7

What is the collision theory?

Answer 7

Reacting particles need to bump into each other but they also need enough energy to react when they collide.

Question 8

What is the activation energy?

Answer 8

Smallest amount of energy that particles must have before they can react.

Question 9

When are reactions most likely to happen between particles?

Answer 9

• increasing the chance of reacting particles colliding with each other
• increasing the energy that they have when they collide

Question 10

What happens when we increase the chance of particles reacting?

Answer 10

The rate of reaction increases.

Question 11

Which has the larger surface area- a log or the same mass of small pieces of wood?

Answer 11

Small pieces of wood.

Question 12

How does the surface area of a solid affects its rate of reaction?

Answer 12

The particles inside a large lump of solid aren’t in contact with the solution so they can’t react. The particles inside the solid have to wait for the particles on the surface to react first.
The smaller the surface area the quicker the reactions take place.

Question 13

Why does increasing the temp increase the rate of reaction?

Answer 13

• particles collide more often

- particles collide with more energy

Question 14

How much does a 10degree rise in temp increase reaction rate at room temp?

Answer 14

Will roughly double.

Question 15

What happens to the time it takes the solution to go cloudy as the temp increases?

Answer 15

Time taken also changes.

Question 16

Why does increasing concentration or pressure increase reaction rate?

Answer 16

Because there are more particles of the reactants moving around in the same volume of solution.

Question 17

Apart from using a catalyst, how can we speed up a reaction?

Answer 17

By using very high temperatures or pressure.

Question 18

How is a catalyst affected by a chemical reactions?

Answer 18

It’s not used up in the reaction so it can be used over and over again.

Question 19

Why is a catalyst in the form of pellets more effective at a whole lump of the catalyst?

Answer 19

Gives them the biggest possible surface area.

Question 20

Why do catalysts save a chemical company money?

Answer 20

Because using high temperatures and pressures often involves burning fossil fuels.

Question 21

What is an example of a very efficient catalyst found in living things?

Answer 21

Enzymes.

Question 22

What do we call a reaction that releases energy to its surroundings?

Answer 22

Exothermic reactions.

Question 23

What do we call a reaction that absorbs energy from its surroundings?

Answer 23

Endothermic reactions.

Question 24

Give two examples of exothermic reactions:

Answer 24

• respiration

- neutralisation

Question 25

Give an example of an endothermic reaction:

Answer 25

-thermal decomposition

Question 26

How does the energy change for a reversible reaction in one directs compare with the energy change for the reaction in the opposite direction?

Answer 26

Releases energy and then absorbs exactly the same amount of energy.

Question 27

What can anhydrous copper surface be used to test for?

Answer 27

Tests for water.

Question 28

Why does blue cobalt chloride turn pink if left out in the open air?

Answer 28

Because water has been added to the paper.

Question 29

When water is added to blue cobalt chloride is energy absorbed or released?

Answer 29

Released.

Question 30

Common salt is used as a catalyst in some disposable hand warmers. What does this mean?

Answer 30

Products use exothermic reactions to warm you up. Salt used is often sodium ethanoate. Dissolve much of the salt as possible in hot water.

Question 31

What processes can be used to cool things down?

Answer 31

Endothermic processes.