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Chemistry GCSE > Analysis > Flashcards

Analysis Flashcards

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1
Q

What is an element?

A
  • atoms with the same atomic number
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2
Q

What is a compound?

A
  • two or more different elements chemically bonded together in fixed proportions as a result of a chemical reaction
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3
Q

What is a mixutre?

A
  • contains 2 or more elements or compounds
  • individual substances are not chemically combined
  • individual components not in fixed proportions
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4
Q

What is a pure substance?

A
  • one element or one compound only
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5
Q

What is the difference between melting and boiling points between pure and impure substances?

A
  • pure - specific melting/ boiling point
  • impure - range of temperatures
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6
Q

What is a formulation?

A
  • mixture that has been designed as a useful product
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7
Q

What is the difference between a formulation and a simple mixture?

A
  • many components
  • fixed proportion of each component
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8
Q

What are some examples of formulations?

A
  • cleaning products
  • fertilisers
  • fuels
  • medicines
  • foods
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9
Q

How are formulations made?

A
  • mixing components in controlled quantities
  • each individual substance has particular purpose
  • so that formulation has desired properties
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10
Q

What does chromatography do?

A
  • separate a mixture of coloured solutes in a solution
  • used to identify substances
  • involves a stationary phase and a mobile phase
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11
Q

What is a stationary phase?

A
  • does not move
  • paper in case of chromatography
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12
Q

What is a mobile phase?

A
  • moves through stationary phase
  • solvent in case of chromatography

water or ethanol could be the solvent

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13
Q

What affects the Rf value of a substance?

A
  • relative strengths of bonds to the mobile or stationary phase
  • stronger bond to mobile phase = longer distance up the paper
  • stronger bond to stationary phase = shorter distance
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14
Q

How do you calculate the Rf value of a substance?

A

Rf = distance moved by substance/ distance moved by solvent

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15
Q

How do you conduct a chromatography?

A

1) draw baseline with pencil (won’t dissolve)
2) add spot of sample to baseline
3) fill beaker with shallow solvent
4) place in solvent
5) remove and dry

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16
Q

How do you identify hydrogen

A
  • hold lit splint near open test tube
  • if “pop” is heard then hydrogen is present
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17
Q

How do you identify oxygen?

A
  • hold glowing splint in test tube
  • if relights then oxygen is present
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18
Q

How do you identify carbon dioxide?

A
  • shake gas with limewater
  • if limewater turns cloudy/ milky then CO2 is present
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19
Q

How do you identify chlorine?

A
  • put damp litmus paper into gas
  • if litmus paper turns white then chlorine is present
20
Q

How do you clean the nichrome wire for a flame test?

A

1) dip loop in dilute hydrochloric acid
2) hold loop in hot part of blue bunsen burner flame
3) repeat 1&2 until there is no extra colour to flame

21
Q

How do you conduct a flame test on a solid sample?

A

using a damp wooden splint

22
Q

How do you test a sample in the flame test?

A

1) dip loop in dilute hydrochloric acid then sample
2) hold loop on edge of blue bunsen flame
3) observe + record colour of flame

23
Q

What colour is the flame when the Li+ cation is present?

A

Crimson

24
Q

What colour is the flame when the Na+ cation is present?

A

yellow

25
Q

What colour is the flame when the K+ cation is present?

A

purple

26
Q

What colour is the flame when the Ca2+ cation is present?

A

orange- red

27
Q

What colour is the flame when the Cu2+ cation is present?

A

green

28
Q

What compounds are soluble in water?

A

most potassim, sodium or lithium compounds

29
Q

What happens when insoluble compounds are produced?

A
  • appear as jelly-like/ cloudy precipitates
30
Q

How do you conduct a precipitate test?

A

1) use clean pipette to transfer 1-2cm^3 of test solution to test tube
2) use another pipette, add few drops of sodium hydroxide solution
3) observe colour of any precipitate
4) if white precipitate forms -> add more sodium hydroxide to see if it dissolves

31
Q

What colour precipitate is produced by the Fe2+ cation?

A

green

32
Q

What colour precipitate is produced by the Fe 3+ cation?

A

brown

33
Q

What colour precipitate is produced by the Mg2+ cation?

A

white

34
Q

What colour precipitate is produced by the Ca+ cation?

A

white

35
Q

What colour precipitate is produced by the Cu 2+ cation?

A

blue

36
Q

What colour precipitate is produced by the Al 3+ cation?

A

white- dissolves in excess sodium hydroxide

37
Q

What is a cation?

A

a positively charged ion

38
Q

What is an anion?

A

a negatively charged ion

39
Q

How do you test for carbonate ions?

A

1) add few drops of dilute hydrochloric acid to solid sample/ solution
2) if carbonate ions are present = bubbles of gas are given off
3) gas may not be carbon dioxide -> limewater test

40
Q

How do you test for halide ions?

A

1) Add a few drops of dilute nitric acid to sample
2) add a few drops of silver nitrate solution
3) observe colour of precipitate formed

41
Q

What colour precipitate is formed with a Cl- ion?

A

white

42
Q

What colour precipitate is formed with a Br- ion?

A

cream

43
Q

What colour precipitate is formed with a I- ion?

A

yellow

44
Q

What are the advantages of instrumental methods of analysis?

A
  • faster
  • sensitive (can detect very small quantities of a substance)
  • accurate (correctly detect & identify substances in sample)
45
Q

What are the disadvantages of flame tests?

A
  • can only detect prescence of metal ions
  • cannot measure concentration
  • uncertain if sample is mixture of metal ions
46
Q

How does flame emission spectroscopy work?

A
  • sample heated in flame
  • thermal energy provided excites electrons in ion -> jump to higher energy levels
  • fall back to lower shells -> emit energy in form of light
  • light emitted passed through spectroscope, intensity + wavelengths used to identify metal ions
  • combination of wavelengths depends of charge of ion + electronic config
  • output = emission spectrum, different ions produce lines in different parts of spectrum
  • line spectrum compared against computer database to identify ion

Chemistry GCSE (10 decks)

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