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Chemistry > C4.2 Identifying the products of chemical reactions > Flashcards

C4.2 Identifying the products of chemical reactions Flashcards

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1
Q

What are positive ions called?

A

Cations

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2
Q

What are negative ions called?

A

anions

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3
Q

What tests are used to identify positive ions ?

A
  • The flame test
  • Sodium hydroxide precipitate
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4
Q

What tests are used to identify negative ions ?

A
  • Testing for halide ions
  • Testing for sulphate ions
  • Testing for carbonate ions
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5
Q

What is the method of the flame test?

A
  • Dip a nichrome wire in hydrochloric acid to clean it
  • Dip the clean wire into the sample
  • Place the wire into the blue bunsen flame and note the colour
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6
Q

Why is a nichrome wire used in the flame test?

A

A nichrome wire is used because its very unreactive and has a high melting point

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7
Q

In the flame test, what colour flag appears when Lithium is present ?

A

Red

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8
Q

In the flame test, what colour flag appears when Sodium is present ?

A

Yellow - Orange

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9
Q

In the flame test, what colour flag appears when Potassium is present ?

A

Lilac

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10
Q

In the flame test, what colour flag appears when Calcium is present ?

A

Red - orange

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11
Q

In the flame test, what colour flag appears when Copper is present ?

A

Green - Blue

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12
Q

What is the method of the Sodium Hydroxide precipitate test?

A
  • Adding a few drops of sodium hydroxide so the solution we are testing
  • Nothing the colour of any precipitate that forms
  • Adding an excess of sodium hydroxide
  • Noting whether the precipitate re-desolves
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13
Q

What is the colour of the precipitate when calcium is present ?

A

White

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14
Q

What is the colour of the precipitate when Zinc is present ?

A

White

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15
Q

What is the colour of the precipitate when Iron ( Fe2+ ) is present ?

A

Green

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16
Q

What is the colour of the precipitate when Iron ( Fe3+ ) is present ?

A

Brown

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17
Q

What is the colour of the precipitate when Copper is present ?

A

Blue

18
Q

What’s a precipitate ?

A

An insoluble solid

19
Q

What are the reactions called from sodium hydroxide precipitate test?

A

Precipitation reactions

20
Q

How are we able to distinguish Zinc or Calcium in the sodium hydroxide precipitate test ?

A

Out of the two, Zinc is the only one that desolves with excess NaOH ( Sodium hydroxide )

21
Q

What metal ion desolves with excess NaOH ( Sodium hydroxide ) ?

A

Zinc

22
Q

What is the method for the test for Sulphate ions ?

A
  • Add 2 drops HCl (aq) ( hydrochloric acid ) - it removes any carbonate ions which would also give a white precipitate
  • Add 2 drops BaCl2 ( aq )
23
Q

What is the equation for testing for Sulphate ions?

A

Ba^2+ (aq) + SOv4^2- (aq) => BaSOv4 (s).

24
Q

What is the method for the test for Carbonate ions ?

A
  • Add acid [ eg. HCl (aq ) ]
  • Bubble any gas produced through lime water
  • If lime water goes cloudy means carbonate ions are personal
25
Q

What is the equation for testing for Carbonate ions?

A

2H^+ (aq) + COv3^2- (aq) –> Hv2O (l) + COv2 (g)

26
Q

What are the results of testing for carbonate ?

A

Results : Observe fizzing because COv2 produced ( limewater turns cloudy )

27
Q

What is the method for the test for halide ions ?

A
  • Add 2 drop of HNOv3 [ dilute nitric acid ] - removes any carbonate ions, which would also give a white precipitate
  • Add 2 drops AgNOv3 (aq) [ silver nitrate solution ]
28
Q

What colour precipitate comes out from silver nitrate + chlorine , bromine , iodine ion ?

A

chlorine –> forms white ppt

Bromine –> forms cream ppt

Iodine –> Forms yellow ppt

29
Q

What colour precipitate comes out from Barium chloride + sulphate ions ?

A

White precipitate

30
Q

How does instrumental analysis compare to other tests?

A
  • Its more accurate
  • Its faster ( and run all the time )
  • Its more sensitive ( can use very small samples )
31
Q

How does infrared spectroscopy work ?

A

Infrared radiation is passed through a sample. Different types of covalent bond absorb different frequencies of infrared, which images the bonds vibrate. The resultant spectrum shows “peaks” which so respond to different types of covalent bonds

32
Q

What does a mass spectrum show?

A
  • The peak with the highest mass to charge ratio is called the molecular ion peak
  • The mass to change ratio ( m/z ) of this peak tells us the relative mass ( Mr ) or the molecule
33
Q

What is gas chromatography ?

A

An instrumental technique that separates mixtures in the gas state

34
Q

How does gas chromatography work?

A
  • The mixture enters the column as a gas and is carried along the carrier gas
  • Components that don’t bond to the silica powder have a short retention time and reach the end of the column quickly
  • Components that bond to the silica powder take a long time to come out ( have a long retention time )
  • At the end of the column is a detector, that makes a graph called a gas chromatogram
35
Q

What is the mobile phase in gas chromatography ?

A

An unreactive carrier gas ( like nitrogen or helium )

36
Q

What is the stationary phase in gas chromatography ?

A

Silica ( or alumina ) powder packed in a metal column

37
Q

What does this gas chromatogram show ?

A
  • 3 peaks = 3 substances in the mixture
  • the furthest peak to the right has the longest retention time
  • the second peak (B) is the tallest peak so there is more substance B
38
Q

How to test for Hydrogen ?

A

A lighted splint will produce a squeaky pop in precense of hydrogen

39
Q

How to test for Oxygen ?

A

A glowing splint reignites the precedes of oxygen

40
Q

How to test for CO2 ?

A

Chemistry (17 decks)

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