Combined Chemistry - C6 The rate and extent of chemical change Flashcards

1
Q

What two equations can be used to measure the rate of a reaction?

A

mean rate of reaction = (quantity of reactant used) / time

mean rate of reaction = (quantity of product formed) / time

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2
Q

Calculate the mean rate of reaction for the following examples (give the correct unit):

a) A reaction producing 50 cm3 of gas in 5 s.
b) A reaction where 5 g of calcium carbonate completely reacts in 10 s.

*These are just examples, you should be able to calculate rate of reactions for any given reactions.

A

a) 10 cm3/s
b) 0.5 g/s

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3
Q

Higher Q. Calculate the rate of reaction when 2 moles of magnesium oxide reacts in 4 seconds.

*This is just an example, you should be able to calculate rate of reactions for any given reactions.

A

0.5 mol/s

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4
Q

Which reaction shows the fastest rate of reaction? A, B or C?

A

A

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5
Q

What is the name for the straight line drawn next to the curve at the point indicated by the arrow?

A

Tangent

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6
Q

Higher Q. How would you calculate the rate of the reaction at the point indicated by the arrow?

A
  • Draw a tangent at that point
  • Calculate the gradient of the tangent
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7
Q

List the 5 things that can affect the rate of a reaction.

A
  • Concentration (of solutions)
  • Pressure (of gases)
  • Surface area (of solids)
  • Temperature
  • Catalysts
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8
Q

What is the name for the minimum amount of energy needed for a reaction to happen?

A

Activation Energy

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9
Q

What theory states that chemical reactions only occur when reacting particles collude with enough energy?

A

Collision Theory

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10
Q

Explain how temperature affects the rate of reaction.

A
  • Increasing temperature…
  • …Increases the frequency of collisions…
  • …The collisions are more energetic.
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11
Q

Explain how surface area affects the rate of reaction.

A
  • Increasing the surface area …
  • …increases the frequency of collisions…
  • …and so increases the rate of reaction.
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12
Q

Explain how concentration affects the rate of reaction.

A
  • Increasing the concentration…
  • …increases the frequency of collisions…
  • …and so increases the rate of reaction.
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13
Q

Explain how pressure affects the rate of reaction.

A
  • Increasing the pressure…
  • …increases the frequency of collisions…
  • …and so increases the rate of reaction.
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14
Q

How does a catalyst work?

A
  • Catalysts increase the rate of reaction…
  • …by providing an alternative pathway for the reaction…
  • …with a lower activation energy.
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15
Q

What is a catalyst?

A

Something that increases the rate of a reaction without being used up in the reaction.

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16
Q

How would you add a line to show the effect of a catalyst on the reaction profile below?

A
17
Q

What is the symbol for a reversible reaction?

A
18
Q

If a reversible reaction is endothermic in forward direction, what will it be in the reverse direction?

A

Exothermic

19
Q

What does ‘equilibrium’ mean?

A

In a reversible reaction, the forward and reverse reactions occur at exactly the same rate.

20
Q

Higher Q. What is Le Chatelier’s Principle?

A

The idea that if you change the conditions(such as temperature and pressure) of a reversible reaction at equilibrium, the system will try to counteract the change.

21
Q

Higher Q. What effect will increasing the concentration of a reactant have on a reversible reaction?

A
  • More products will be formed
  • Until equilibrium is reached again
22
Q

Higher Q. For a gaseous reaction at equilibrium, what would be the effect of…

a) … increasing pressure
b) … decreasing pressure

A

a) Equilibrium position will shift towards the side with the smaller number of molecules
b) Equilibrium position will shift towards the side with the larger number of molecules

23
Q

Higher Q. For a reversible reaction at equilibrium, what effect will increasing temperature have on…

a) … the endothermic reaction
b) … the exothermic reaction

A

a) Endothermic reaction: The amount of product increases
b) Exothermic reaction: The amount of product decreases

24
Q

Higher Q. For a reversible reaction at equilibrium, what effect will decreasing temperature have on…

a) … the endothermic reaction
b) … the exothermic reaction

A

a) Endothermic reaction: The amount of product decreases
b) Exothermic reaction: The amount of product increases