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GCSE Chemistry > C12 - Chemical Analysis > Flashcards

C12 - Chemical Analysis Flashcards

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1
Q

What is a volumetric pipette?

A

A glass tube used to measure accurate volumes of liquids

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2
Q

What is R𝒻 (Retention Factor) ?

A

A measurement from chromatography: it is the distance a spot of substance has been carried above the baseline divided by the solvent front

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3
Q

What is the test from Carbon Dioxide Gas?

A

Bubble through limewater, limewater turns cloudy white if Carbon Dioxide is present

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4
Q

What is the test for hydrogen gas?

A

Hold a lit splint near the gas being tested, a “pop” noise will be made if hydrogen is present

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5
Q

What is the test for Chlorine Gas?

A

Chlorine gas will bleach damp indicator paper

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6
Q

What is the test for oxygen gas?

A

A glowing splint will relight if exposed to oxygen

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7
Q

What is the test for Lithium ions?

A

Hold in a roaring Bunsen flame, the flame will turn Crimson Red if lithium is present

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8
Q

What is the test for sodium ions?

A

Hold in a roaring Bunsen flame, the flame will turn Yellow-orange if Sodium is present

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9
Q

What is the test for potassium ions?

A

Hold in a roaring Bunsen flame, the flame will turn Lilac if Potassium is present

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10
Q

What is the test for copper ions?

A
  • Hold in a roaring Bunsen flame, the flame will turn green if copper is present
  • Add to a solution of sodium hydroxide, a blue precipitate will form if copper is present
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11
Q

What is the test for Calcium ions?

A
  • Hold in a roaring Bunsen flame, the flame will turn orange-red if Calcium is present
  • Add to a solution of sodium hydroxide, a white precipitate that does not dissolve when more NaOH is added will form if calcium is present
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12
Q

What is the test for Magnesium ions?

A

*Add to a solution of sodium hydroxide, a white precipitate that does not dissolve when more NaOH is added will form if magnesium is present

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13
Q

What is the test for Aluminium Ions?

A

*Add to a solution of sodium hydroxide, a white precipitate that dissolves when more NaOH is added will form if Aluminium is present

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14
Q

What is the test for Iron (II) ions?

A

*Add to a solution of sodium hydroxide, a green precipitate will form if Iron (II) is present

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15
Q

What is the test for Iron (III) ions?

A

*Add to a solution of sodium hydroxide, a brown precipitate will form if Iron (III) is present

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16
Q

What is the test for Carbonate ions?

A
  • Add to a dilute acid, bubbles of gas that turn limewater cloudy will form if Carbonate ions are present
  • Add to a solution of barium chloride with hydrochloric acid, bubbles of gas will form when acid is added if Carbonate ions are present
  • Add to a solution of silver nitrate with nitric acid, bubbles of gas will form when acid is added if Carbonate ions are present
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17
Q

What is the test for Chloride ions?

A
  • Add to a solution of Silver Nitrate with Nitric acid, a white precipitate will form if chloride ions are present
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18
Q

What is the test for Bromide ions?

A
  • Add to a solution of Silver Nitrate with Nitric acid, a cream precipitate will form if Bromide ions are present
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19
Q

What is the test for Iodide ions?

A
  • Add to a solution of Silver Nitrate with Nitric acid, a yellow precipitate will form if Iodide ions are present
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20
Q

Describe how to carry out a flame test:

A

Place a damp splint into some of the ionic compound as a solid. Place the splint in the roaring Bunsen flame and look for any colour

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21
Q

Describe how to carry out the cation test with sodium hydroxide:

A

Dissolve a small amount of the solid ionic compound in deionised water (about 3cm depth). Then add sodium hydroxide solution. If a white precipitate forms, test it further by adding more sodium hydroxide solution.

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22
Q

Describe how to carry out the halide ion test:

A

Dissolve a small amount of solid ionic compound in deionised water (about 3cm depth). Then add a few drops of nitric acid followed by 1cm depth of silver nitrate solution

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23
Q

Describe how to carry out the sulfate ions test:

A

Dissolve a small amount of the solid ionic compound in deionised water (about 3cm depth). Then add a few drops of hydrochloric acid followed by 1cm depth of barium chloride solution

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24
Q

Describe how to carry out the carbonate ion test:

A

Place some hydrochloric acid in a test tube and add a small spatula load of the solid ionic compound. Look for bubbles of gas. If a gas is released then insert a delivery tube into the test tube and bubble the gas through limewater

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25
Q

What is the ionic equation of when copper ions are added to a solution of sodium hydroxide?

A

Cu²⁺(aq) + 2OH⁻(aq) -> Cu(OH)₂(s)

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26
Q

What is the ionic equation of when Calcium ions are added to a solution of sodium hydroxide?

A

Ca²⁺(aq) + 2OH⁻(aq) -> Ca(OH)₂(s)

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27
Q

What is the ionic equation of when Magnesium ions are added to a solution of sodium hydroxide?

A

Mg²⁺(aq) + 2OH⁻(aq) -> Mg(OH)₂(s)

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28
Q

What is the ionic equation of when Aluminium ions are added to a solution of sodium hydroxide?

A

Al³⁺(aq) + 3OH⁻(aq) -> Al(OH)₃(s)

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29
Q

What is the ionic equation of when Iron (II) ions are added to a solution of sodium hydroxide?

A

Fe²⁺(aq) + 2OH⁻ -> Fe(OH)₂(s)

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30
Q

What is the ionic equation of when Iron (III) ions are added to a solution of sodium hydroxide?

A

Fe³⁺(aq) + 3OH⁻ -> Fe(OH)₃(s)

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31
Q

What is the ionic equation of when Sulfate ions are added to a solution of Barium Chloride with hydrochloric acid?

A

Ba²⁺(aq) + SO₄²⁻(aq) -> BaSO₄(s)

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32
Q

What is the ionic equation of when Chloride ions are added to a solution of Silver Nitrate with nitric acid?

A

Ag⁺(aq) + Cl⁻(aq) -> AgCl(s)

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33
Q

What is the ionic equation of when Bromide ions are added to a solution of Silver Nitrate with nitric acid?

A

Ag⁺(aq) + Br⁻(aq) -> AgBr(s)

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34
Q

What is the ionic equation of when Iodide ions are added to a solution of Silver Nitrate with nitric acid?

A

Ag⁺(aq) + I⁻(aq) -> AgI(s)

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35
Q

Why is hydrochloric acid added before barium chloride when testing for Sulfate?

A

The hydrochloric acid is added first to remove any carbonate ions that might be present - they would also produce a white precipitate, giving a false positive result.

36
Q

Why is nitric added before silver nitrate when testing for halides?

A

The nitric acid is added first to remove any carbonate ions that might be present - they would produce a white precipitate of silver carbonate, giving a false positive result for chloride ions.

37
Q

A sample of compound A was heated in a Bunsen flame and no flame colour. On addition of sodium hydroxide solution to a solution of A, a white precipitate formed that did not re-dissolve when more sodium hydroxide was added. When nitric acid was added to a solution of A, the mixture bubbled giving a gas that turned limewater cloudy. What is the formula of the compound?

A

MgCO₃

38
Q

A sample of compound A was heated in a Bunsen flame and gave a green flame. On addition of sodium hydroxide solution to a solution of A, a blue precipitate formed. When nitric acid and silver nitrate was added to a solution of A, a white precipitate formed. What is the formula of the compound?

A

CuCl₂

39
Q

What are the advantages of chemical analysis techniques?

A
  • Quick to carry out
  • Cheap
  • No training required
40
Q

What are the disadvantages of chemical analysis techniques?

A
  • Destructive
  • Less accurate
  • Difficult to test small amounts
  • Qualitative data (Not quantitative)
  • Limited number of ions which can be tested
41
Q

What are the advantages of instrumental analytical techniques?

A
  • More accurate
  • Not Destructive
  • Can detect from small samples
  • Quantitative data
42
Q

What are disadvantages of instrumental analytical techniques?

A
  • Expensive

* Requires special training

43
Q

What is an example of an instrumental analytical technique?

A

Flame emission spectroscopy

44
Q

What is the difference between a continuous spectrum and a line spectrum?

A

Continuous spectrum contains all wavelengths of light whereas the emission line spectrum only shows specific wavelengths of light

45
Q

How does flame emission spectroscopy identify which metal ions are present in a sample?

A

The sample is heated in a flame and the light emitted is viewed through a spectroscope. Each metal ion produces its own characteristic pattern of lines as each metal ion emits light over different wavelengths when heated. The pattern is known as its line spectrum and can be used to identify the metal ion by comparing it with a database held on a computer.

46
Q

How can the concentration of ions be obtained from flame emission spectroscopy?

A

The concentration of the ions is determined by the intensity of the lines (faint or solid line)

47
Q

Why can a simple flame test not identify whether 2 ions where in a mixture?

A

A flame test can only identify 1 ion, this may be because 1 flame may mask another or the colours may mix - giving an inaccurate result

48
Q

Why is flame emission spectroscopy used in the steel industry?

A

They use flame emission spectroscopy to identify the composition of the steel as steel is a mixture of different metals

49
Q

Why is flame emission spectroscopy used by water industries?

A

They use flame emission spectroscopy to identify the concentration of ions within the water

50
Q

Some tests were carried out on ionic substance A. Addition of sodium hydroxide solution to a solution of A gave a white precipitate that redissolved when more sodium hydroxide was added. Addition of acidified silver nitrate solution to a solution of A gave a cream precipitate. What is the compound formula?

A

AlBr₃

51
Q

What is a pure subtance?

A

A substance containing only 1 type of substance, it is either an element or a compound and it melts/boils at a specific temperature

52
Q

What is a mixture?

A

A mixture is a substance that is made up of 2 or more chemical substances that are not chemically bonded together and melts/boils over a range of temperatures

53
Q

What is a formulation?

A

A mixture made up of definite proportions that has been designed as a useful product

54
Q

How are formulations made?

A

Formulations are made by mixing the components in carefully measured quantities to ensure that the product has the required properties

55
Q

What are some examples of formulations?

A
  • Fuels
  • Cleaning agents
  • Paints
  • Medicines
  • Alloys
  • Food and drinks
  • Fertilisers
56
Q

How can mixtures be separated?

A

Mixtures can be separated by physical processes which do not involve chemical reactions and NO new substances are made. Separation techniques include:

  • Filtration
  • Crystallisation
  • Simple Distillation
  • Fractional Distillation
57
Q

What is filtration used to separate?

A

Insoluble substances from a solvent (Which may contain soluble subtances)

58
Q

What is crystallisation used to separate?

A

A soluble solid (solute) from a solvent

59
Q

What is Simple Distillation used to separate?

A

The solvent from the solute

60
Q

What is fractional distillation used to separate?

A

Mixtures of miscible liquids

61
Q

Why is fractional distillation used over simple distillation when separating mixtures of miscible liquids?

A

Fractional distillation is able to separate mixtures containing substances with very close boiling points, whereas simple distillation can only separate substances with a greater range between the boiling points

62
Q

Describe how Filtration works:

A

There are tiny holes in the filter paper which allow the solute and the solvent to pass through. However, the insoluble substance cannot pass through the filter paper and is therefore collected on the filter paper as residue.

63
Q

Describe how Crystallisation works:

A

The solution is heated using a water bath to evaporate the water in the solution. Heating is stopped at the point of crystallisation (when you can first see small crystals). The rest of the water in the solution is left to evaporate at room temperature to leave crystals to form

64
Q

Describe how Simple Distillation works:

A

The solution is heated and boiled to evaporate the solvent. The vapour then enters a condenser. This is an outer glass tube with water flowing through it that acts as a cooling “jacket” around the inner glass tube. The hot vapour is cooled and condensed back into a liquid for collection in a receiving vessel. The solid solute will remain in the heated flask

65
Q

Describe how fractional distillation in a classroom works:

A

The miscible liquids have different boiling points, so you can use this to distil off and collect the liquid with the lowest boiling point first. The vapours must pass over and between glass beads in the fractionating column before they reach the condenser. The temperature in the fractionating column is greater at the bottom, getting lower as vapours rise up. The substance with the higher boiling point will condense more readily and drip back down into the flask beneath. The substance with the lower boiling point will continue to rise and pass over the condenser, where it is cool enough to condense into a liquid and be collected

66
Q

Label this filtration equipment:

A
67
Q

Label this crystallisation equipment:

A
68
Q

Label this distillation equipment

A
69
Q

Label this fractional Distillation equipment:

A
70
Q

What is a compound?

A

Substances which contain 2 or more types of atoms chemically bonded together

71
Q

What is a molecule?

A

A substance which contains 2 or more atoms chemically bonded together using covalent bonds

72
Q

Why is salt placed on the roads in winter months?

A

Salt may be placed on the road before ice has formed as salt lowers the freezing point of water, preventing ice from forming on the roads even if temperatures fall below 0*C. It may also increase friction between the road and tyre.

73
Q

Why is pure gold not suitable for jewellery and why is an alloy suitable?

A

Pure gold is very soft and malleable. An alloy contains differently sized atoms as it contains a mixture of elements. This disrupts the regular arrangement of atoms in an alloy, meaning the layers cannot slide over each other as easily. This makes the alloy stronger and harder than a pure metal. It may also combine useful properties such as chemical or corrosion resistant.

74
Q

Why is the starting line drawn with pencil in chromatography?

A

Graphite is insoluble in the solvent and therefore will not run, remaining where it is.

75
Q

Why is the level of the solvent below the level of the starting / sample line in chromatography?

A

So the samples do not dissolve into the beaker below

76
Q

Explain why different samples move at different speeds and different distances during paper chromatography:

A

Different substances have different relative attraction for the mobile and stationary phases. A substance with a stronger relative attraction to the mobile phase than the stationary phase moves faster and further than one with a weaker relative attraction to the mobile phase than the stationary phase

77
Q

Explain why sample 1 has a different R𝒻 value in different solvents

A

Substance 1 has a stronger relative attraction to water compared to the paper than it does for ethanol compared to the paper. This means that it travels further in the water, therefore it has a greater R𝒻 value

78
Q

What are fixed points?

A

The melting and boiling points of an element or compound

79
Q

What is a test to discover whether a substance is pure or a mixture?

A

If pure, it will melt/boil at exactly 1 temperature, whereas a mixture will melt/boil over a range of temperatures

80
Q

What do impurities in a substance cause?

A
  • The melting point lowers

* The boiling point increases

81
Q

What may paint contain?

A
  • Pigments - to provide colour
  • A binder - to help the paint attach to an object
  • A solvent - to help the pigment and binder spread well
82
Q

What is the mobile phase in paper chromatography?

A

The solvent - the mobile phase moves through the stationary phase, carrying the components of the mixture

83
Q

What is the stationary phase in paper chromatography?

A

The paper

84
Q

What is the equation for retention factor?

A

R𝒻 = Distance moved by substance / distance moved by solvent

85
Q

Why can you not use sulfuric acid instead of hydrochloric acid in the test for sulfate ions?

A

Sulfuric acid contains sulfate ions, therefore a false positive may occur

86
Q

What is a line spectrum?

A

The characteristic pattern of wavelengths of light emitted by a metal during flame emission spectroscopy

87
Q

What ion always comes first in a chemical formula of an ionic substance?

A

The positive ion (cation)

GCSE Chemistry (15 decks)

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