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Chemistry Paper 2 > Topic 8 Chemical Analysis > Flashcards

Topic 8 Chemical Analysis Flashcards

1
Q

What is a pure substance?

A

Single element/compound, not mixed with any other substance

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2
Q

What will a chemically pure substance melt and boil at?

A

Specific temperatures

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3
Q

How can you test the purity of a sample?

A

Measuring melting or boiling point, compare with melting or boiling point of pure substance

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4
Q

What will impurities in a sample do to the melting point?

A

Lower, increase melting range

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5
Q

What will impurities in a sample do to the boiling point?

A

Increase, sample may boil at range of temperatures

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6
Q

What is a formulation?

A

Mixture designed as a useful product

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7
Q

How are formulations made?

A

Mixing components in carefully measured quantities to ensure product has required properties

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8
Q

What are 7 examples of formulations?

A

Foods
Cleaning agents
Paints
Medicines
Alloys
Fertilisers
Fuels

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9
Q

What is the mobile phase in chromatography?

A

Molecules can move, liquid or gas

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10
Q

What is the stationary phase in chromatography?

A

Molecules can’t move, solid or really thick liquid

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11
Q

What is the stationary phase in paper chromatography?

A

Chromatography paper

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12
Q

What is the mobile phase in paper chromatography?

A

Solvent (ethanol/water)

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13
Q

What 2 things does the amount of time the molecules spend in each phase in paper chromatography depend on?

A

How soluble they are in solvent
How attracted they are to paper

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14
Q

What will happen to molecules with higher solubility in solvent and less attracted to paper in paper chromatography?

A

Spend more time in mobile phase, carried further up paper

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15
Q

What is the test for hydrogen?

A

Hold lit splint at open end of test tube of gas, hydrogen burns rapidly with pop sound

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16
Q

What is the test for oxygen?

A

Insert glowing splint into test tube of gas, splint relights in oxygen

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17
Q

What is the test for carbon dioxide?

A

Bubbling co2 through/shaking co2 with aqueous solution of calcium hydroxide (limewater), turns cloudy

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18
Q

What is the test for chlorine?

A

Damp litmus paper put into chlorine gas, litmus paper bleached and turns white

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19
Q

What are cations?

A

Positive (metal) ions

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20
Q

What are the 2 ways we can test for cations?

A

Flame tests
Sodium hydroxide solution

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21
Q

Which 5 metal compounds produce distinctive colours in flame tests?

A

Lithium
Sodium
Potassium
Calcium
Copper

22
Q

What colour flame will copper ions produce?

23
Q

What colour flame will sodium ions produce?

24
Q

What colour flame will calcium ions produce?

A

Orange-red

25
Q

What colour flame will lithium ions produce?

26
Q

What colour flame will potassium ions produce?

27
Q

What reagent can we use to identify some metal ions (cations)?

A

Sodium hydroxide solution NaOH

28
Q

What colour precipitate will copper ions produce?

29
Q

What colour precipitate will magnesium ions produce?

30
Q

What colour precipitate will calcium ions produce?

31
Q

What colour precipitate will aluminium ions produce?

A

White, then dissolves in excess NaOH to form colourless solution

32
Q

What colour precipitate will iron 2+ ions produce?

33
Q

What colour precipitate will iron 3+ ions produce?

34
Q

How can we test for sulphate ions?

A

Barium chloride solution in presence of dilute hydrochloric acid

35
Q

What is the formula for a sulphate ion?

36
Q

What colour precipitate will sulphate ions make with acidified barium chloride?

37
Q

What is an anion?

A

Negative ion

38
Q

How can we test for carbonates?

A

React with dilute acid to form CO2, CO2 identified with limewater

39
Q

How can we test for halides?

A

Silver nitrate solution in presence of dilute nitric acid

40
Q

Which 3 halide ions produce precipitates with acidified silver nitrate?

A

Chloride
Bromide
Iodide

41
Q

What colour precipitate do chloride Cl- ions make with acidified silver nitrate?

42
Q

What colour precipitate do bromide Br- ions make with acidified silver nitrate?

43
Q

What colour precipitate do iodide I- ions make with acidified silver nitrate?

44
Q

What is the equation to calculate the Rf value?

A

Rf= distance travelled by solvent (B)/ distance travelled by solvent (A)

45
Q

What is flame emission spectroscopy an example of?

A

Instrumental method

46
Q

What can chemists use to detect and identify elements instead of conducting tests?

A

Instrumental methods (tests that use machines)

47
Q

What are 3 advantages of using instrumental methods (machines)?

A

Accurate
sensitive
Rapid

48
Q

What can flame emission spectroscopy be used to identify?

A

Different metal ions in solutions

49
Q

What are the 5 steps in flame emission spectroscopy?

A
  1. Sample put in flame
  2. Ions heat up, electrons excited, electrons drop back to original energy levels
  3. Transfer energy as light
  4. Light passed through spectroscope
  5. Detects different wavelengths of light, produce line spectrum
50
Q

Why does each ion produce a different pattern of wavelengths and has a different line spectrum in flame emission spectroscopy?

A

Ions have different charges and electron arrangements, different ions emit different wavelengths of light

51
Q

What does the intensity of the line spectrum indicate in flame emission spectroscopy?

A

Concentration of ion

52
Q

What 2 things can line spectrums be used to identify in flame emission spectroscopy?

A

Ions in solution
Calculate concentrations

Chemistry Paper 2 (5 decks)

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