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Chemistry > Rate Of Reactions > Flashcards

Rate Of Reactions Flashcards

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0
Q

How can the rate be found?

A

By measuring how much of a reactant is used or how much of a product is formed, and the time taken.

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1
Q

What does the rate of a reaction measure?

A

It measures the speed of a reaction or how fast it is.

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2
Q

What is the alternative rate for finding the rate?

A

By measuring the time taken for a certain amount of reactant to be used or product to be formed. This gives an average rate for the time measured.

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3
Q

How can the average rate also be found?

A

By measuring the time it takes for a certain amount of solid to appear in a solution.

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4
Q

How could you find the average rate if a gas is given off in the reaction?

A

You could measure the time taken to collect a certain amount of gas.

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5
Q

What two types of measurement must be made to find the average rate of a reaction?

A

The amount (of product or reactant) and time

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6
Q

What piece of information can be found from the gradient or slope of the line on a graph of amount of reactant or product again time?

A

The rate of reaction

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7
Q

Fill in the gap:

The steeper the gradient the __________ the reaction is at that time.

A

Faster

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8
Q

To produce a graph what will you have to measure?

A

You will have to measure the mass of gas released or the volume of gas produced at intervals of time.

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9
Q

What other things could you measure over time?

A

Changes in colour
Concentration
pH of a reaction

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10
Q

What does the gradient of a line tell us?

A

The gradient or slope of the line on a graph of amount of reactant or product against time tells us the rate of reaction at that time. The steeper the gradient, the faster the reaction.

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11
Q

What does the collision theory state?

A

That reactions can only happen if particles collide.

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12
Q

Fill in the gaps:

Particles must collide with a certain amount of ________ before they can _______.

A

Energy

React

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13
Q

Why must the particles collide with enough energy?

A

So that they can change into new substances.

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14
Q

What do we call the minimum energy needed for particles to react?

A

The activation energy

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15
Q

What is the activation energy?

A

The minimum amount of energy that particles must have in order to react.

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16
Q

Give some factors that increase the chance of collisions , or energy of the particles that will increase the rate of reaction.

A 
Increasing the temperature
Increasing concentration of solution 
Increasing pressure of gases
Increasing SA of solids
Using a catalyst
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17
Q

Fill in the gaps:

The ________ the powder the faster the reaction.

A

Finer

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18
Q

Fill in the gaps:
Breaking large pieces of solid into smaller pieces exposes new surfaces and so _________ the surface area. This means there are more ___________ in the same time. So a powder reacts faster than large lumps of a substance.

A

Increases

Collisions

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19
Q

What does increasing the surface area mean?

A

Making the pieces smaller.

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20
Q

What does increasing the temperature do to the particles?

A

It increases the speed of the particles in a reaction mixture.

21
Q

If the speed of the particles increases what does this mean?

A

It means they’ll collide more often which increases the rate of reaction.

22
Q

Fill in the gaps:

As well as colliding more frequently they collide with more _________, which also ________ the rate of reaction.

A

Energy

Increases

23
Q

Do reactions happen more quickly if you increase the temperature?

A

Yes

24
Q

If you increases the temperatures by 10°C what happens to the rate of reaction?

A

It will roughly double the rate of reaction, so they go twice as fast.

25
Q

What happens if you decrease the temperature?

A

The rate of reaction slows down

26
Q

Why do we refrigerate or freeze food?

A

Because lower temperatures slow down reactions so it’ll stay fresh for longer.

27
Q

Why does a small change in temperature have a large effect on the rate of reaction?

A

It increases the frequency if collisions and the energy of the particles.

28
Q

Give a brief description of the particles in cold and hot temperatures.

A

Cold- slow movement, less energy and less frequent collisions
Hot- fast movement ,more energy , and more frequency collisions

29
Q

What are the particles in a solution doing?

A

Moving around randomly

30
Q

What does it mean if the concentration of a solution is increased?

A

It means there are more particles dissolved in the same volume. This means the dissolved particles are closer together and they collide more often.

31
Q

What happens if the concentration of a solution is increased?

A

More particles dissolved in same volume and therefore more closer together so more collisions.

32
Q

Why does increasing the concentration of a reactant increase the rate of reaction?

A

Because the particles collide more frequently

33
Q

Why do reactions in solutions go faster at higher concentrations?

A

It increases the frequency of collisions.

34
Q

What happens if you increase the pressure of a gas?

A

It puts more molecules into the same volume and so they collide more frequently. This increases the rate of reactions that have gases as reactants.

35
Q

Why does increasing the pressure increase the rate of reaction of two gases?

A

The frequency of collisions increases because there are more molecules in the same volume.

36
Q

What is a catalyst?

A

A substance that speeds up a chemical reaction. At the end of the reaction the catalyst remains chemically unchanged.

37
Q

What do catalysts do?

A

Change the rates of chemical reactions.

38
Q

What are catalysts used for?

A

Speeding up reactions

39
Q

What else do catalysts do? (Hint: activation energy)

A

Catalyst lower the activation energy of the reaction so that more of the collisions result in my reaction.

40
Q

What happens at the end of a reaction to the catalyst?

A

It is left at the need and so it can be used over and over again.

41
Q

Why can catalysts be used over and over again?

A

They remain at the end of a reaction or they are not used up in the reaction.

42
Q

What are catalysts(think s,l,g )

A

Solids

43
Q

Do catalysts work with different types of reactions?

A

No

44
Q

What do different reactions need?

A

Different catalysts

45
Q

Why do different reactions need different catalysts?

A

Catalysts only work with one type of reaction.

46
Q

Why are catalysts used in industrial processes?

A

Because they can reduce the energy and time needed for reactions. This helps to reduce costs and reduce impacts on the environment.

47
Q

What are the benefits of using catalysts in industrial processes?

A

They reduce the energy needed and the time needed, and so reduce costs. They may reduce the amount of fossil fuel used and so conserve resources and reduce pollution.

48
Q

In the industry what do many of the catalysts involve?

A

Transition metals and their compounds.

49
Q

Give one disadvantage of transition metal catalysts.

A

They may be toxic or expensive.

50
Q

Name an example of a catalyst

A

Enzymes-biological catalysts

51
Q

What two areas of research offer possibilities for new or better catalysts?

A

Nanoscience and enzymes

Chemistry (11 decks)

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