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Flashcards in C2.4 Deck (31)
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1
Q

What do we mean by the rate of chemical reaction?

A

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

2
Q

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

A

Have to make money by producing useful products.

3
Q

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

A
  • how quickly the reactants are used up as they make products
  • how wicket the products of the reaction are made
4
Q

What is the equation of rate of reactions?

A

=amount of reactant used or product formed/time

5
Q

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

A
  • temperature
  • surface area
  • concentration of solution or pressure of gasses
  • presence of a catalyst
6
Q

When do reactions take place?

A

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

7
Q

What is the collision theory?

A

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

8
Q

What is the activation energy?

A

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

9
Q

When are reactions most likely to happen between particles?

A
  • increasing the chance of reacting particles colliding with each other
  • increasing the energy that they have when they collide
10
Q

What happens when we increase the chance of particles reacting?

A

The rate of reaction increases.

11
Q

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

A

Small pieces of wood.

12
Q

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

A

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.

13
Q

Why does increasing the temp increase the rate of reaction?

A
  • particles collide more often

- particles collide with more energy

14
Q

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

A

Will roughly double.

15
Q

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

A

Time taken also changes.

16
Q

Why does increasing concentration or pressure increase reaction rate?

A

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

17
Q

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

A

By using very high temperatures or pressure.

18
Q

How is a catalyst affected by a chemical reactions?

A

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

19
Q

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

A

Gives them the biggest possible surface area.

20
Q

Why do catalysts save a chemical company money?

A

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

21
Q

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

A

Enzymes.

22
Q

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

A

Exothermic reactions.

23
Q

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

A

Endothermic reactions.

24
Q

Give two examples of exothermic reactions:

A
  • respiration

- neutralisation

25
Q

Give an example of an endothermic reaction:

A

-thermal decomposition

26
Q

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

A

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

27
Q

What can anhydrous copper surface be used to test for?

A

Tests for water.

28
Q

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

A

Because water has been added to the paper.

29
Q

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

A

Released.

30
Q

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

A

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

31
Q

What processes can be used to cool things down?

A

Endothermic processes.