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A Level / GCSE Chemisty > Ion Tests > Flashcards

Ion Tests Flashcards

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1
Q

What are the different tests for metal cations?

A
  • flame test
  • (flame photometry/ flame emission spectroscopy)
  • precipitation reactions
  • ammonium ion test
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2
Q

What cations can the flame test indicate?

A
  • Lithium (Li+)
  • Sodium (Na+)
  • Potassium (K+)
  • Calcium (Ca2+)
  • Copper (Cu2+)
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3
Q

What colour will lithium cations show in a flame test?

A

Red (crimson)

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4
Q

What colour will sodium cations show in a flame test?

A

Yellow

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5
Q

What colour will potassium cations show in a flame test?

A

Lilac

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6
Q

What colour will calcium cations show in a flame test?

A

Orange-red

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7
Q

What colour will copper cations show in a flame test?

A

Blue-green

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8
Q

Why might the instrumental method - a flame photometer - be used instead of the flame test to recognise the cations?

A
  • speed
  • sensitivity (detect tiny amounts)
  • accuracy
    (It overcomes problems of comparing similar ones, when low concentration + when samples contain multiple metal cations)
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9
Q

What does flame photometry involve?

A

A spectroscope - detects individual wavelengths emitted (which are unique to each) which are emitted when the metal cations are heated

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10
Q

What does the intensity (dull/bright) of lines indicate in flame photometry?

A

The concentration of the metal cation

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11
Q

What can be used (with flame photometry) to identify cations + their concentrations in unknown samples?

A

Known metal cation spectra

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12
Q

What does a calibration curve allow us to determine?

A

The concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples

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13
Q

What are precipitation reactions used to identify?

A

Dissolved metal cations - they produce precipitates

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14
Q

What does a precipitation reaction involve?

A

Sodium hydroxide solution is added to test solutions to produce a hydroxide precipitate

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15
Q

What cations can a precipitation reaction be used to identify?

A
  • Iron (II) (Fe2+)
  • Iron (III) (Fe3+)
  • Copper (Cu2+)
  • Calcium (Ca2+)
  • Aluminium (Al3+)
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16
Q

What colour is the hydroxide precipitate for iron (II) (iron hydroxide) cations in the precipitation reaction?

A

Green

17
Q

What colour is the hydroxide precipitate for iron (III) (iron hydroxide) cations in the precipitation reaction?

A

Brown

18
Q

What colour is the hydroxide precipitate for copper (copper hydroxide) cations in the precipitation reaction?

A

Blue

19
Q

What colour is the hydroxide precipitate for calcium (calcium hydroxide) cations in the precipitation reaction?

A

White

20
Q

What colour is the hydroxide precipitate for aluminium (aluminium hydroxide) cations in the precipitation reaction?

A

White

21
Q

The precipitate for both calcium and aluminium in the precipitation reactions test is white. How can they be distinguished from one another?

A
  • add excess sodium hydroxide solution
  • aluminium - precipitate dissolves to form colourless solution
  • calcium - precipitate uncharged (remains in excess)
22
Q

What is the symbol for ammonium ions?

A

NH4^+

23
Q

How are ammonium ions tested for? (Ammonia has characteristic sharp smell, but confirmatory gas is used to identify gas)

A
  • add dilute sodium hydroxide solution
  • warm mixture -> ammonia gas (NH3) is formed
  • the gas will change damp red litmus paper blue
24
Q

What is another test for ammonium ions?

A
  • a glass rod dipped in concentrated hydrochloric acid
  • held near mouth of test tube containing mixture
  • ammonium chloride formed as white smoke
25
Q

What are the tests for non-metal anions?

A
  • carbonates (CO3^2-)
  • sulfates
  • halides (chloride ions, bromide ions, iodide ions)
26
Q

What is the test for carbonate anions?

A
  • add hydrochloric acid
  • bubble through limewater
  • lime water turns cloudy if carbon dioxide (therefore carbonate) is present
27
Q

What is the test for sulphate anions?

A
  • add dilute hydrochloric acid to remove impurities (eg. carbonate ions)
  • add barium chloride
  • white precipitate forms (barium sulfate) if sulfate anions are present
28
Q

What is the test for halide anions?

A
  • add dilute nitric acid to remove impurities

- silver nitrate added to produce precipitate

29
Q

What colour precipitate is formed for chloride anions in the test for halides?

A

White (silver chloride)

30
Q

What colour precipitate is formed for bromide anions in the test for halides?

A

Cream (silver bromide)

31
Q

What colour precipitate is formed for iodide anions in the test for halides?

A

Yellow (silver iodide)

32
Q

Test for carbon dioxide

A

Bubble through limewater - turns cloudy

33
Q

Test for oxygen

A

Glowing splint relights

34
Q

Test for hydrogen

A

Lit splint - squeaky pop

35
Q

Test for chlorine

A

Bleaches damp blue litmus paper

A Level / GCSE Chemisty (26 decks)

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