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GCSE Chemistry > Rate And Extent Of Chemical change > Flashcards

Rate And Extent Of Chemical change Flashcards

1
Q

How can you measure rate of reaction?

A

By measuring the quantity of a reactant used or the quality of product formed over time

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2
Q

Equation to determine mean rate of reaction using a reactant

A

Mean rate = quantity of a reactant used ÷ time

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3
Q

Equation to determine mean rate of reaction using product

A

Mean rate = quantity of products formed ÷ time

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4
Q

How to calculate mean rate of reaction from a graph?

A

Rate (gradient) = change in y ÷ change in x

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5
Q

Calculate the mean rate of reaction that produces 52 cm³ of gas in 2 minutes

A

52 ÷ 2 = 26cm³/min (could convert minutes to seconds so can use centimetres cubed per seconds units)

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6
Q

How do you measure the amount of reactant or product made in a reaction?

A

Mass in g
Volume in cm³

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7
Q

What are the units for rate of reaction?

A

g/s using mass
Or
cm³/s using volume

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8
Q

What are the units for rate using moles?

A

mol/s

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9
Q

How can you measure the rate of reaction from a graph at a specific time?

A

Draw a tangent and determine the gradient

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10
Q

When drawing a tangent, how should the ruler be positions on the graph?

A

Place a ruler on the curve at the point where you want to know the slope. The space between the ruler and the curve should be equal on both sides of the point

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11
Q

What does the steepness of the slope on a rate graph tell you?

A

How fast the reaction is, the steeper of the slope, faster the reaction

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12
Q

How can you tell from a rate graph that the reaction has finished

A

The graph becomes flat

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13
Q

How can you measure rate?

A

Loss in mass of reactants or
Volume of gas produced or
Time for a solution to become opaque (cloudy) or coloured

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14
Q

What piece of equipment can you use to measure the volume of gas made?

A

Gas syringe or “ overwater” using an upturned, measuring cylinder in a water trough

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15
Q

What are factors can affect the rate of a chemical reaction?

A

Concentration
Pressure
surface area
Temperature
Catalyst

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16
Q

What is collision theory?

A

Reactants must collide with enough energy (activation energy)

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17
Q

What is activation energy?

A

The minimum amount of energy of the particles must have to react

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18
Q

What must particles have when they collide?

A

Sufficient amount of energy (activation energy)

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19
Q

What does increasing temperature do in terms of collisions?

A

Rate increases, because particles move faster
So more frequent collisions
And more particles are colliding with energy greater than activation energy

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20
Q

What does increasing concentrations do in terms of collisions?

A

More particles in a given volume
More frequent successful collisions

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21
Q

How can you increase the surface area of a solid?

A

Break up the solid into small pieces/make it into a powder

22
Q

What does increasing pressure do in terms of collisions?

A

Particles are moves closer together
More frequent, successful collisions

23
Q

What is a catalyst?

A

A substance which increases the rate of chemical reactions
But are not used up during the reaction
Different reactions need different catalysts

24
Q

What is an enzyme?

A

A biological catalyst

25
Q

How do catalysts increase the rate of reaction?

A

They provide a different pathway for the reaction that has a lower activation energy

26
Q

Are catalysts included in chemical equations

A

No

27
Q

What is a reversible reaction? What symbol is used to represent this?

A

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

⇌

28
Q

Why does the amount of products and reactants remain the same equilibrium?

A

The rate of forward reaction is equal to the rate of backward to reaction
So the concentrations of products and reactants. Stay constant.

29
Q

An equation to show the reversible reaction when ammonium chloride is heated

A

Ammonium chloride ⇌ ammonia + hydrogen chloride

—> heat
<— cool

30
Q

How does a reaction reach equilibrium?

A

When a reversible reaction occurs in a closed system and the forward and backwards reactions happen at exactly the same rate

31
Q

What is a closed system?

A

When it is sealed, products or reactants, cannot enter or leave

32
Q

How can you change the direction of a reversible reaction?

A

By changing are the conditions of:
Temperature
Pressure
Concentration

33
Q

If a reversible reaction is exothermic in one direction, What will the opposite direction be?

A

Endo thermic

34
Q

What is the amount of energy like in both directions in a reversible reaction?

A

The same

35
Q

An equation to show how hydrated copper sulphate can be heated to give anhydrous copper sulphate

A

Hydrated copper sulfate (blue) ⇌ anhydrous copper sulphate (white) + water

36
Q

What is equilibrium

A

When the forwards and reverse reactions happen at exactly the same rate (when in a closed system so the reactants abs products can’t escape from the reactants)

37
Q

What is Le Chateliers principal?

A

At equilibrium, if the conditions change it will shift to oppose these changes (it wants to try and get back to equilibria again).

38
Q

What happens if the concentration of one of the reactants or products is changed

A

This system is no longer at equilibrium, and the concentrations of all substances will change until equilibrium is reached again

39
Q

What happens when the concentration of reactants are increased?

A

More products will be made to get rid of extra reactants added

40
Q

What happens when the concentration of the products are decreased?

A

More reactants will react to get more products again

41
Q

What happens if the temperature is increased

A

The equilibrium will always move in the endothermic direction

42
Q

What happens if the temperature is decreased?

A

The equilibrium will always move in the exothermic direction

43
Q

What happens if the temperature is increased for an endothermic reaction?

A

It was shift in favour of the endothermic reaction as it wants to cool back down

44
Q

What happens if the temperature is decreased for an endothermic reaction?

A

It will shift in favour of the exothermic reaction as it wants to heat back up

45
Q

What happens if the temperature is increased for an exothermic reaction?

A

It will shift in favour of the endothermic reaction as it wants it to cool back down

46
Q

What happens if the temperature is decrease are an exothermic reaction

A

It will shift in favour of the exothermic reaction as it wants to heat back up

47
Q

If a change in pressure occurs, what do you look at?

A

The number of GASEOUS MOLES on reactants vs products

Eg N2(g) + 3H2(g) ⇌ 2NH3(g)

There are four moles of gas on the reactant side
There are 2 moles of gas on the products side

48
Q

What happens if pressure is increased in an equilibrium

A

Equilibrium shift towards the side with the least number of gaseous molecules

49
Q

What happens if pressure is decreased in an equilibrium

A

Equilibrium will shift towards the side with the most number of gaseous molecules

50
Q

What affect does pressure have if the same number of moles in the reactants and the products

A

None, no affect

51
Q

What effect does catalyst have on position of an equilibrium?

A

None as speeds up both the rate of forwards and backwards reactions equally

GCSE Chemistry (8 decks)

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