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AQA GCSE Chemistry > Titrations > Flashcards

Titrations Flashcards

1
Q

What are the three stages to titration?

A
  • Filling the burette
  • Filling the pipette
  • Titration process
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2
Q

Describe the first stage of titration:

A
  • Wash the burette first with water and then acid
  • Fill burette (with X) using a filter funnel on the floor
  • Remove the bubble
  • Remove filter funnel and set meniscus to zero
  • Record intial reading (0.00)
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3
Q

Describe the second stage of titration:

A
  • Put pipette filler onto pipette
  • Expel air from filler and suck up (acid/alkali) to the meniscus
  • put acid/alkali into conical flask on a white tile
  • add 4 drops of phenolphthalein indicator
  • swirl together
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4
Q

Describe the third stage of titration:

A
  • Add acid/alkali to the conical flask from the burette whilst constantly swirling
  • When signs as to a colour change begin, start dripping the acid/alkali into the flask
  • Stop adding acid when there is a colour change
  • Record the final value on the burette
  • Substract the inital value from the final value
  • Repeat the experiment
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5
Q

What are the names of the values calculated during titrations?

A

titre values (final titre-initial titre)

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6
Q

What is done with the titre values once collected?

A

A mean titration value is calculated by ignoring the first titre value and using only those which are concordant (within 0.10 ml of eachother)

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7
Q

What is the titre?

A

Volume of liquid in the burette

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8
Q

Why is the first titre value never used when calculating a mean?

A

To reduce inaccuracy as it is only a rough value

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9
Q

How do you calculate the moles?

A

Concentration x volume

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10
Q

What is volume measured in?

A

dm^3

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11
Q

How is the concentration calculated in g/dm^3?

A

Relative molecular mass x concentration in mol/dm^3

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12
Q

What is the relationship between titre value and the type of acid?

A

Doubling the number of hydrogen ions (in the acid), halves the titre value

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13
Q

What are the four common errors in titration experiments?

A
  • Not swirling the conical flask
  • Not removing the filter funnel before dispensing liquid from burette
  • Not removing the bubble below the tap
  • Paralax error
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14
Q

Why is not swirling the conical flask an error in titration?

A

Because the swirling mixes the hyrogen ions and hydroxide ions to allow the even spread of the reaction otherwise the titre value increases

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15
Q

Why is not removing the filter funnel an error in titration?

A

Because some acid will remain on the funnel and drip into the burette, increasing the titre value.

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16
Q

Why is not removing the bubble an error in titration?

A

Because some acid will be used to fill the bubble, increasing the titre value

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17
Q

Why is a paralax error an error in titration?

A

Readings should be taken at eye level and the burrette should be perpendicuar else the titre value will be skewed.

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18
Q

What is the type of pipette used in titrations?

A

Bulb pipette

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19
Q

What is the fixed volume of a bulb pipette?

A

25.0 cm^3

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20
Q

What does a mole signify?

A

The number of particles present

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21
Q

What is the maximum volume for a burette?

A

50.0 cm^3

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22
Q

How is uncertainty calculated in a titration?

A

Range/2

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23
Q

What is a salt?

A

A compound where a metal ion replaces a hydrogen ion

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24
Q

What does soluble mean?

A

Dissolves in water

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25
Q

What are the soluble bases?

A
  • Group 1 metal hydroxide/oxide/carbonate

- Ammonium hydroxide

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26
Q

What are the insoluble bases?

A
  • Group 2 or 3 hydroxide/oxide/carbonate

- transition metal hydroxides/oxides/carbonates

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27
Q

What is aqueous ammonia?

A

Ammonium hydroxide

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28
Q

What happens to ammonia in water?

A

It reacts to make ammonium hydroxide

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29
Q

Describe the method by which a neutralisation experiment is carried out to obtain salt crystals:

A
  • Measure hydrochoric acid into beaker and gently warm with Bunsen burner
  • remove beaker from heat and add a spatula full of coper oxide to acid and stir until it is in excess
  • pour solution into new beaker through funnel with filter paper to remove excess CuO
  • pour this filtrate into an evaporating basin and place basin on top of a water bath
  • evaporate half the water and check for crystallisation point, using a cold glass stirring rod
  • cool and allow to crystalise. pat crystals dry between two peices of filter paper
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30
Q

Why is an acid heated before adding the base?

A

To increase the solubility of the acid so it is easier for it to dissolve the base

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31
Q

Why is the base put in excess into the acid?

A

So that all of the acid reacts

32
Q

Why are the reactants stirred?

A

So they can mix

33
Q

Why is the solution filtered?

A

To obtain the salt solution (filtrate)

34
Q

Why is the solution put in an evaporting basin on a water bath?

A

To evaporate the water from the salt solution

35
Q

Why is the crystallisation point checked?

A

As the crystallosation point exists when the solution is saturated

36
Q

What does allowing the evaporated filtrate to cool do?

A

Allows crystals to form - slower cooling = larger crystals

37
Q

Why must sulfuric acid be heated gently?

A
  • for safety as it is highly corrosive

- when overheated, sulfur dioxide released would be harmful to lungs if inhaled

38
Q

What does in excess mean?

A

Greater mass of the reactant than is necessary to react completely with the limiting reagent

39
Q

State the law of the conservation of mass

A

No atoms are made or lost during a reaction

40
Q

What is a redox reaction?

A

Acid + Metal = Metal Salt + Hydrogen

41
Q

What is a neutralisation reaction?

A

Acid + Alkali = Salt + Water

42
Q

Why is a pipette used in a titration?

A

As it delivers a fixed volume of liquid

43
Q

Why is a burette used in a titration?

A

As it delivers a variable volume (ranges 0.05 to 50 cm^3)

44
Q

Why is a conical flask used in a titration?

A

It is used whilst swirling liquid to avoid spills

45
Q

Why must an indicator like universal indicator not be used in a titration?

A

As universal indicator gives a gradual colour change and the indicator in a titration must give a sharp colour change

46
Q

What colour is methyl orange in acid? Alkali?

A

Acid-orange

Alkali-yellow

47
Q

What colour is phenolphthalein in acid? Alkali?

A

Acid- colourless

Alkali - purple

48
Q

Define strong acid:

A

completely ionises when in an aqueous solution

49
Q

Define weak acid:

A

partially ionises when in an aqueous solution

50
Q

Define concentrated:

A

a large number of particles per unit volume

51
Q

Define dilute:

A

A small number of particles per unit volume

52
Q

What is a base?

A

A proton acceptor

53
Q

What is an acid?

A

A proton donor

54
Q

What is a strong base?

A

A base which completely ionises in an aqueous solution

55
Q

What is a weak base?

A

A base which partially ionises in an aqueous solution

56
Q

Why is the maximum temperature increase higher when a more concentrated solution is used compared to the same overall moles at a slower addition rate?

A

Because the number of moles reacting is the same but the total volume is less

57
Q

After a substance is added in excess, why does the temperature of the reaction decrease?

A

Because the cool/cooler substance absorbs energy and lowers the temperature

58
Q

Why would the alkali be added in excess in a neutralisation reaction?

A

To ensure all the acid is used up

59
Q

What are reasons as to why the yield of a reaction isn’t 100%?

A
  • reaction does not go to completion
  • competing reactions which could be unexpected
  • loss of material when transferring products or separating them
  • reaction is reversible
60
Q

How are salt crystals obtained from a solution?

A
  • evaporate half the water

- leave to crystallise

61
Q

What is the empirical formula?

A

The simplest whole number ratio of the elements in a compound

62
Q

What is the molecular formula?

A

The total numbr of elements in a compound

63
Q

Why is low atom economy not usually profitable?

A
  • means more raw materials are needed which may be more expensive
  • inefficient way of using raw materials which can be non-renewable
  • reactions produce more waste which can be expensive to get rid of
64
Q

What can be done to increase the profitablity of low atom economy?

A

selling the waste/bi products of the reaction

65
Q

What do high atom economy reactions tend to be ? Explain this

A

Sustainable - they use up as little of the earth’s resources as possible and put as few chemicals into the envirnoment

66
Q

What is the theoretical yield?

A

The maximum mass of a product you would get if all the reactants form the desired products and none of the products are lost

67
Q

How do you calculate moles of anything?

A

mass/Mr

68
Q

How do you calculate the moles of a gas?

A

voulme/24

69
Q

What does mass equal?

A

Mr x mol

70
Q

What is the law to do with gases in equal amounts?

A

Equal amounts (in moles) of gases occupy the same volume under the same conditions of temperature and pressure

71
Q

What is the volume of one mole of any gas at room temperature and pressure?

A

24 dm^3

72
Q

What is relative formula mass?

A

the sum of all the relative atomic masses of all the atoms in the compound

73
Q

How is the uncertainty of a measurement reduced?

A

By repeating it and calculating a mean

74
Q

What is the limiting reactant?

A

the reactant that is completely used up in the reaction

75
Q

Why do the products after heating a metal have a greater mass than that of the initial metal?

A
  • one or more of the reactants is a gas
  • all the products are solids, liquids or aqeuous
  • particles in a gas move around and fill the space they are in
  • so before the reaction, gas is floating in the air but does not add to the mass of the metal
  • when the gas reacts to form part of the product, the particles become contained inside the reaction vessel so the total mass of the reaction vessel increases
76
Q

Define acid:

A

Something which produces hydrogen ions in an aqeous solution

77
Q

What is the advantage of a burette?

A

It can deliver a variable volume of a liquid

AQA GCSE Chemistry (10 decks)

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