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AQA GCSE Chem!! > Chemical Analysis: Identification of Ions > Flashcards

Chemical Analysis: Identification of Ions Flashcards

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1
Q

potassium ions

A

K+

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2
Q

what colour flame do potassium ions produce?

A

lilac

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3
Q

copper ions

A

Cu2+

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4
Q

what colour flame do copper 2+ ions produce?

A

green

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5
Q

sodium ions

A

Na+

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6
Q

what colour flame do sodium ions produce?

A

yellow

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7
Q

calcium ions

A

Ca2+

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8
Q

what colour flame do calcium ions produce?

A

orange-red flame

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9
Q

lithium ions

A

Li+

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10
Q

what colour flame do lithium ions produce?

A

crimson

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11
Q

why are flame tests used?

A

to identify metal ions in ionic compounds

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12
Q

flame test practical steps

A
  1. submerge nichrome wire loop in dilute HCl to clean it
  2. place nichrome wire into sample being tested
  3. hold nichrome wire loop in bunsen burner’s blue flame
  4. observe change in colour of bunsen burner flame
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13
Q

what colour precipitate do magnesium ions (Mg2+) form?

A

white precipitate magnesium hydroxide

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14
Q

magnesium hydroxide equation

A

Mg2+ (aq) + 2OH- (aq) –> Mg(OH)2 (s)

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15
Q

what colour precipitate do aluminium ions (Al3+) form?

A

white precipitate aluminium hydroxide

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16
Q

aluminium hydroxide equation

A

Al3+ (aq) + 3OH- (aq) –> Al(OH)3 (s)

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17
Q

what does aluminium hydroxide dissolve in?

A

excess NaOH (forms colourless solutions)

18
Q

what colour precipitate do calcium ions (Ca2+) form?

A

white precipitate calcium hydroxide

19
Q

calcium hydroxide equation

A

Ca2+ (aq) + 2OH- (aq) –> Ca(OH)2 (s)

20
Q

what colour precipitate do iron ions (Fe2+) form?

A

green precipitate iron (II) hydroxide

21
Q

iron (II) hydroxide equation

A

Fe2+ (aq) + 2OH- (aq) –> Fe(OH)2 (s)

22
Q

what colour precipitate do iron ions (Fe3+) from?

A

brown precipitate iron (II) hydroxide

23
Q

iron (III) hydroxide equation

A

Fe3+ (aq) + 3OH- (aq) –> Fe(OH)3 (s)

24
Q

what colour precipitate do copper ions (Cu2+) form?

A

blue precipitate copper (II) hydroxide

25
Q

copper (II) hydroxide equation

A

Cu2+ (aq) + 2OH- (aq) –> Cu(OH)2 (s)

26
Q

Test for carbonates?

A
  • add dilute acid to sample
  • CO2 will be produced, observed by effervescence
  • bubble gas through limewater to test it
27
Q

what do all carbonates produce?

A

CO3 2-

28
Q

how to test for halides?

A
  • add dilute nitric acid to unknown solution (removes carbonate ions to ensure they don’t form a precipitate)
  • add dilute silver nitrate
  • if halide ions are present, they will form a white precipitate with silver ions
29
Q

what colour precipitate is silver chloride?

A

white

30
Q

silver chloride equation

A

Ag+ (aq) + Cl- (aq) –> AgCl (s)

31
Q

what colour precipitate is silver bromide?

A

cream

32
Q

silver bromide equation

A

Ag+ (aq) + Br- (aq) –> AgBr (s)

33
Q

what colour precipitate is silver iodide?

A

pale yellow

34
Q

silver iodide equation

A

Ag+ (aq) + I- (aq) –> AgI (s)

35
Q

how to test for sulfates?

A
  • add dilute HCl to unknown sample (removes carbonate ions which could disrupt results by forming a precipitate)
  • add barium chloride solution
  • white precipitate forms if sulfates are present
36
Q

what colour precipitate does barium sulphate form?

A

white

37
Q

barium sulphate equation

A

Ba2+ (aq) + SO4 2- (aq) –> BaSO4 (s)

38
Q

advantages of using instrumental methods of chemical analysis

A

greater sensitivity and accuracy
- quicker at producing results
- able to analyse tiny samples

39
Q

disadvantages of using instrumental methods of chemical analysis

A
  • expensive
  • must go through special training to operate the instruments
  • only useful when compared to data from known substances
40
Q

how does flame emission spectroscopy work?

A
  1. place sample of metal solution being tested into a flame, light will be given off
  2. light given off is captured in a spectroscope - instrument generates a line spectrum by distinguishing between light with different wave lengths
41
Q

what does a flame emission spectroscopy analyse?

A
  • identity of metal ions (metal ions generate new lines on spectrum so can identify all ions present in solution)
  • concentration of metal ions (intensity of line)
  • reference spectra (analyse mixtures by comparing them with reference spectra)

AQA GCSE Chem!! (1 decks)

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