6. The Rate and Extent Of Chemical Change Flashcards

1
Q

How do you work out rate?

A

Rate = quantity of reactants used / time

or

Rate = quantity of products used / time

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2
Q

What does the collision theory state?

A

In order for a chemical reaction to occur, particles must collide with sufficient energy

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3
Q

What is activation energy?

A

The minimum energy particles must have for a reaction to be successful

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4
Q

What happens as a reaction progresses?

A

The concentration of reactants decreases meaning the frequency of collisions between particles is reduced and so the reaction slows down

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5
Q

How is the rate of a reaction increased?

A
  • particles must collide more frequently

* particles must collide with more energy

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6
Q

How do you achieve a higher rate of reaction?

A

Increase pressure, temperature, or concentration

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7
Q

What is concentration?

A

The number of reactant particles in a given volume of liquid

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8
Q

Does increasing temperature increase the number of reacting particles?

A

No, it just increases the chance of successful collisions

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9
Q

Will the amount of product produced in the reaction be more, less, or the same at a higher temperature?

A

The same amount of product will be produced at all temperatures just at different rates

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10
Q

What is a catalyst?

A

A substance that changes the rate of reactions, but is not changed chemically itself at the end of the reaction

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11
Q

How do catalysts work?

A
  • do not increase frequency of collisions or make collisions more energetic
  • do provide an alternate reaction pathway to the products with a lower activation energy
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12
Q

What is a reversible reaction?

A

Where the products of the reaction can react to produce the original reactants

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13
Q

How can reversible reactions be represented?

A

A + B equilibrium arrow symbol C + D

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14
Q

What does the double arrow on a reaction mean?

A

The reaction can go in either direction

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15
Q

What happens if a reversible reaction in exothermic in one direction?

A

It is endothermic in the other

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16
Q

What does it mean in a reversible reaction that the reaction is exothermic in one direction and endothermic in the other?

A

The energy absorbed in one direction is equal to the energy released in the other

17
Q

What is an example of a reversible reaction?

A

Hydrated copper sulphate <> anhydrous copper sulphate + water

18
Q

What always happens when a reversible reaction takes place in a closed system?

A

A state of equilibrium will be reached

19
Q

What is equilibrium?

A

When the amounts of reactants and products reach a balance - their concentrations stop changing

20
Q

What is a closed system?

A

When none of the reactants or products can escape

21
Q

How are the rates of the forward and backward reactions in a state of equilibrium?

A

The rate of the forward reaction is equal to the rate of the backward reaction

22
Q

Why are the conditions of equilibrium changed?

A

In industrial processes, to:

  • maximise yield
  • minimise cost
  • minimise environmental impact
23
Q

What does the position of equilibrium depend on?

A
  • temperature
  • pressure
  • concentration
24
Q

What is Le Chatelier’s rule?

A

If a system is at equilibrium and a change is made to any of the conditions then the system responds to counteract the change

25
Q

What is said when an equilibrium shifts so the forward reaction is favoured? (reactants -> products)

A

We say equilibrium is shifted to the right so more products are made

26
Q

What is said when an equilibrium shifts so the backward reaction is favoured? (products -> reactants)

A

We say equilibrium is shifted to the left so more reactants are made

27
Q

What happens when a change is made to a reaction which is in equilibrium?

A

The equilibrium position will move to minimise the change made

28
Q

What happens if you raise the temperature of a system (exothermic direction) in equilibrium?

A
  • it will try cool itself down
  • energy is taken in during endothermic reactions
  • endothermic reaction is favoured and yield of endothermic reaction will increase
29
Q

What happens if you decrease the temperature of a system in equilibrium?

A
  • it will try to heat itself up
  • energy is given out during exothermic reaction
  • exothermic reaction is favoured and yield of exothermic will increase
  • equilibrium will shift in exothermic direction
30
Q

What happens if you raise the pressure of a system in equilibrium?

A

The system will try to reduce the pressure

31
Q

Which reaction will be favoured when a system in equilibrium has its pressure raised?

A

The reaction which has fewer molecules of gas produced will be favoured

32
Q

What happens if you lower the pressure of a system in equilibrium?

A

The system will try to increase the pressure

33
Q

Which reaction will be favoured when a system in equilibrium has it’s pressure lowered?

A

The reaction which has more molecules of gas produced will be favoured

34
Q

What happens to the position of equilibrium when concentration is increased?

A

The equilibrium is sent towards the opposite side

35
Q

What happens to the position of equilibrium when the concentration is decreased?

A

The equilibrium is sent towards the same side

36
Q

What does adding a catalyst do to equilibrium?

A
  • doesn’t change equilibrium position
  • both forward and backward reaction increase at the same rate
  • equilibrium is reached faster