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iGCSE Chemistry > 4.3 Rates > Flashcards

4.3 Rates Flashcards

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1
Q

How does increasing temperature increase rate of reaction?

A

particles gain more kinetic energy

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2
Q

How does increasing concentration increase rate of reaction?

A

more particles in the same volume

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3
Q

How does reducing particle size increase the rate of reaction?

A

increases surface area
more contact between reactants

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4
Q

How does using a catalyst increase the rate of reaction?

A

reduces activation energy, provides alternative path

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5
Q

How does changing pressure increase rate of reaction?

A

same particles in smaller volume

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6
Q

What is collision theory?

A

particles must collide with required energy (activation energy) for the reaction

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7
Q

What is activation energy?

A

amount of energy particles need to react

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8
Q

What is collision frequency?

A

how often particles collide with each other

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9
Q

What is percentage success?

A

what percentage of collisions have enough energy

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10
Q

What factors affect rate of reaction?

A

pressure
concentration
surface area
catalyst
temperature

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11
Q

What factors affect collision frequency?

A

concentration
pressure
surface area

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12
Q

What factors affect percentage success?

A

temperature
catalyst

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13
Q

Name an experiment to measure the effect of surface area on rate

A

marble chip experiment

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14
Q

Name an experiment to measure the effect of temperature on rate

A

magnesium and acid experiment

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15
Q

Name an experiment to measure the effect of catalyst on rate

A

hydrogen peroxide experiment

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16
Q

Why are catalysts not included in the equation?

A

because they are unchanged in the reaction

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17
Q

Which catalyst is used in the hydrogen peroxide experiment?

A

manganese oxide

18
Q

How is the scientist able to retrieve the catalyst?

A

it is not used up in the reaction

19
Q

What is a catalyst?

A

substance that increases rate of reaction but remains chemically unchanged

20
Q

How do catalysts work?

A

provide an alternative pathway
percentage of collisions with enough energy is higher
more successful collisions

21
Q

Name an experiment that can demonstrate the effect of concentration on rate

A

disappearing cross experiment

22
Q

What is the disappearing cross experiment?

A

react sodium thiosulphate
solution with hydrochloric acid

23
Q

In the disappearing cross experiment, which solid is produced?

A

sulphur

24
Q

What is the equation for the disappearing cross experiment?

A

sodium thiosulphate + hydrochloric acid -> sulphur + water + sulphur dioxide

25
Q

In the disappearing cross experiment, what is the independent variable?

A

concentration of sodium thiosulphate

26
Q

In the disappearing cross experiment, what is the dependent variable?

A

time taken for cross to disappear

27
Q

In the disappearing cross experiment, what are the control variables?

A

volume of solution
concentration of HCl
temperature

28
Q

What does the disappearing cross experiment prove?

A

rate is proportional to concentration

29
Q

What is the magnesium and acid experiment?

A

reacting magnesium with hydrochloric acid

30
Q

Why does the cross disappear in the disappearing cross experiment?

A

sulphur is produced
in suspension - makes solution cloudy so cross is not visible under breaker anymore

31
Q

In the magnesium and acid experiment, what is the independent variable?

A

temperature of HCl

32
Q

In the magnesium and acid experiment, what is the dependent variable?

A

time take for Mg to disappear

33
Q

In the magnesium and acid experiment, what are the control variables?

A

mass and surface area of Mg
volume and concentration of HCl

34
Q

What is the equation for the magnesium and acid experiment?

A

magnesium + hydrochloric acid -> magnesium chloride + hydrogen

35
Q

What does the magnesium and acid experiment prove?

A

temperature is not proportional to rate

36
Q

What is the equation for rate of a reaction?

A

rate = collision frequency x percentage success

37
Q

What is the hydrogen peroxide experiment?

A

hydrogen peroxide broken down into water and oxygen

38
Q

What is the equation for the hydrogen peroxide experiment?

A

hydrogen peroxide -> water + oxygen
catalysed by manganese oxide

39
Q

In the hydrogen peroxide experiment what is the independent variable?

A

catalyst being used

40
Q

In the hydrogen peroxide experiment what is the dependent variable?

A

volume of oxygen produced

41
Q

What are the control variables in the hydrogen peroxide experiment?

A

volume and concentration of hydrogen peroxide
temperature
mass and surface area of catalyst

42
Q

What does the hydrogen peroxide experiment prove about rate?

A

catalyst increases rate

iGCSE Chemistry (17 decks)

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