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AQA GCSE Chemistry (9-1) > 8. Chemical Analysis > Flashcards

8. Chemical Analysis Flashcards

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1
Q

What is a pure substance?

A

Made up of just one substance - either an element or a compound

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2
Q

How are properties changed when impurities are introduced?

A
  • conductivity
  • strength
  • melting and boiling point
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3
Q

What happens when salt is added to pure water?

A

The salt dissolve to produce an impure substance (salt lowers the temperature of ice) so melts the ice

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4
Q

Difference between melting/boiling point between pure and impure substances?

A

Pure substances melt at a specific temperature whereas impure substances can melt or boil at a range of temperatures

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5
Q

How does melting point of an impure substance compare to that of a pure one?

A

Impure substances have lower melting points than pure substances

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6
Q

What is a formulation?

A

A mixture of compounds/substances that do not react with each other but produce a mixture to suit a particular use

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7
Q

Examples of formulations?

A

Toothpaste, moisturiser, make up, alloys, paint, medicines

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8
Q

What does pure mean in advertising?

A

Nothing else has been added to the product

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9
Q

What are some different types of food additives?

A

Preservatives, colourings, flavour enhancers

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10
Q

What is chromatography?

A

A technique for separating mixtures into their components in order to analyse, identify, purify the mixture or components

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11
Q

What is the mobile phase in chromatography?

A

The solvent (e.g. water)

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12
Q

What is the stationary phase in chromatography?

A

The paper

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13
Q

What is Rf factor?

A

Distance substances move up the paper in a certain amount of time

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14
Q

How to work out Rf factor?

A

Distance moved by substance / distance moved by solvent

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15
Q

What is the solvent front?

A

Point at which water stops moving up the paper

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16
Q

What is the centre spot?

A

Point at which a band or spot of colour is

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17
Q

What is the baseline?

A

Line where original sample was placed

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18
Q

How is chlorine tested for?

A

Electrolysis

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19
Q

How is carbon dioxide tested for?

A

Limewater turns cloudy

Hydrochloric acid + calcium carbonate

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20
Q

How is oxygen tested for?

A

Glowing splint relights

Hydrogen peroxide -> water + oxygen

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21
Q

How is hydrogen tested for?

A

Squeaky pop test

Mg + HCl -> MgCl + H2

22
Q

Ways to test for positive ions?

A

Flame test and sodium hydroxide/precipitate test

23
Q

What is the flame test?

A

Using the colour of the Bunsen flame to identify the metal ion in the compound

24
Q

What does a crimson flame show?

A

Lithium present

25
Q

What does a yellow flame show?

A

Sodium present

26
Q

What does a lilac flame show?

A

Potassium present

27
Q

What does a red flame show?

A

Calcium present

28
Q

What do the flame colours show is present?

A

Crimson - lithium

Yellow - sodium

Lilac - potassium

Red - calcium

29
Q

How to carry out the precipitate test?

A

Add 1cm3 of NaOH solution, if precipitate is white add an excess of NAOH solution

30
Q

What do coloured precipitates show in the sodium hydroxide test?

A

Blue - copper

Green - iron (II)

Brown - iron (III)

31
Q

What does a blue precipitate show in a test for positive ions?

A

Copper present

32
Q

What does a green precipitate show in a test for positive ions?

A

Iron (II) present

33
Q

What does a brown precipitate show in a test for positive ions?

A

Iron (III) present

34
Q

What does a white precipitate show in a test for positive ions?

A

Either aluminium, calcium or magnesium

35
Q

What does a soluble white precipitate show in a test for positive ions?

A

Aluminium present

36
Q

What does an insoluble white precipitate show in a test for positive ions?

A

Either calcium or magnesium present

37
Q

What is a halide?

A

A charged halogen

38
Q

What are the tests for negative ions?

A

Halide test, carbonate test and sulphate test

39
Q

What is the halide test?

A

Add dilute nitric acid and silver nitrate solution - if precipitate forms a halide is present

40
Q

What does a yellow precipitate show in the halide test?

A

Iodide ions present

41
Q

What does a cream precipitate show in the halide test?

A

Bromide ions present

42
Q

What does a white precipitate show in the halide test?

A

Chloride ions present

43
Q

What is the sulphate test?

A

Add dilute HCl then barium chloride soliton - white precipitate show sulphate ions present

44
Q

What does a white precipitate show in the sulphate test?

A

Shows sulphate ions are present

45
Q

What is the carbonate test?

A

Add dilute HCl - bubbles produced = use teat pipette to transfer gas produced to limewater - limewater milky means carbonate ions present

46
Q

What does milky limewater mean in the carbonate test?

A

Carbonate ions are present

47
Q

How can substances be analysed?

A

Using a methods including paper chromatography, gas chromatography, mass spectrometry and flame emission spectroscopy

48
Q

How is flame emission spectroscopy carried out?

A

Sample is put into flame and then the light given off is passed through a spectroscope

49
Q

What is the output in flame emission spectroscopy?

A

A line spectrum that can be analysed to identify metal ions and concentration

50
Q

Advantages of flame emission spectroscopy?

A
  • quick
  • accurate
  • sensitive - only requires a small sample
  • brightness of spectrum = concentration
51
Q

Disadvantages of flame emission spectroscopy?

A
  • destructive- sample being tested is burned

* only identifies presence of elements not compounds

52
Q

Application of flame emission spectroscopy?

A
  • quality control in chemical manufacture
  • working out composition of distant stars
  • drug detection

AQA GCSE Chemistry (9-1) (10 decks)

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