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chemistry > chemical analysis (paper 2) > Flashcards

chemical analysis (paper 2) Flashcards

1
Q

what is a pure substance

A

a substance that contains only one element or compound

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2
Q

what is an impure substance

A

a mixture of elements and compounds

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3
Q

describe the melting point and boiling point of a pure substance

A

has a specific melting point or boiling point, so the temperature stays the same when changing state

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4
Q

describe the melting and boiling point of an impure substance

A

does not have a specific melting point or boiling point, it has a range

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5
Q

what is a formulation

A

a mixture that has been designed as a useful product

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6
Q

examples of formulations

A

paint

cleaning agents

medicines

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7
Q

what is the stationary phase in chromatography

A

the chromatography paper

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8
Q

what is the mobile phase in chromatography

A

the solvent

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9
Q

how do you calculate the Rf value

A

distance moved by the solvent

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10
Q

what is the test and positive result for carbon dioxide gas

A

test - bubble the gas through limewater

positive result - cloudy . milky

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11
Q

what is the test and positive result for oxygen gas

A

test - glowing splint in gas

positive result - relights

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12
Q

what is the test and positive result for hydrogen gas

A

test - put a lit splint into gas

positive result - squeaky pop

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13
Q

what is the test and positive result for chlorine gas

A

test - damp blue litmus paper into gas

positive result - bleaches the litmus paper white

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14
Q

what is the flame test used to test for

A

metal ions

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15
Q

what is the method for the flame test

A

1 - clean a platinum or nichrome wire, using concentrated hydrochloric acid, then place it into the Bunsen burner flame

2 - repeat this until the wire does not produce any colour in the flame

3 - with the clean wire, moisten it in the hydrochloric acid and then dip the wire into the solid, place the wire into the roaring blue flame and observe the colour of the flame

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16
Q

what are you testing for by adding sodium hydroxide

A

metal ions

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17
Q

what do aluminum, magnesium and calcium form when sodium hydroxide is added

A

form white precipitates that are an insoluble metal hydroxide

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18
Q

copper + sodium hydroxide solution

A

pale blue precipitate of Cu(OH)2 forms

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19
Q

iron (2+) + sodium hydroxide solution

A

dirty green precipitate of Fe(OH)2 forms

20
Q

iron (3+) + sodium hydroxide solution

A

rusty brown precipitate of Fe(OH)3 forms

21
Q

test for halide ions and the positive result

A

test - add silver nitrate (AgNO3)

positive result - forms a precipitate

22
Q

what is the colour of the chloride precipitate formed

A

white

23
Q

what is the colour of the bromide precipitate formed

A

cream

24
Q

what is the colour of the iodide precipitate formed

A

yellow

25
Q

what is the test and positive result for carbonate ions

A

test - add hydrochloric acid, a gas is made, bubble the gas through limewater

positive result - turns cloudy

26
Q

test and positive result for sulphate ions

A

test - add hydrochloric acid and barium chloride

positive result - white precipitate (BaS04)

27
Q

flame colour if lithium is present

A

red

28
Q

flame colour if sodium is present

A

yellow

29
Q

flame colour if potassium is present

A

lilac

30
Q

flame colour if calcium is present

A

orangey red

31
Q

flame colour if copper is present

A

green

32
Q

method for the flame test to identify the ions in an unknown substance

A

1 - pour about 1cm depth of each of the labelled chloride solutions into five test tubes in the rack

2 - dip the nichrome wire into the first solution, then hold the tip of the wire in a blue Bunsen burner flame

3 - record observation in a table

4 - clean the wire

5 - repeat steps above for the 4 other substances

6 - empty and clean the test tubes

33
Q

method for the carbonate test when identifying ions in an unknown substance

A

1 - pour about 1cm depth of each of the labelled sodium solutions into the five test tubes in the rack

2 - place 1cm depth of limewater in a sixth test tube

3 - add 1cm depth of dilute hydrochloric acid to each sodium salt solution in turn

4 - only if you see bubbles, quickly use the teat pipette to transfer the gas produced to the limewater, you should pipette the gas into the limewater solution

5 - you will need to take several pipettes of the gas coming off at the surface to get a change in limewater

6 - record your results in a table

34
Q

what will happen to the limewater in the carbonate test if carbonate ions are present

A

bubbles, limewater turns cloudy

35
Q

what will happen to the limewater in the carbonate test if either sulphate, chloride, bromide, iodide ions are present

A

no result

36
Q

method for the sulphate test when identifying ions in an unknown solution

A

1 - pour about 1cm depth of each of the labelled sodium solutions into the five test tubes in the rack

2 - add a few drops of dilute hydrochloric acid to each solution , then add 1cm depth of barium chloride solution

3 - record observations and empty and clean the test tubes

37
Q

what observation will you make if sulphate ions are present during the sulphate test

A

a white precipitate will form

38
Q

what observation will you make if carbonate, chloride, bromide or iodide ions are present during the sulphate test

A

no result

39
Q

method for the halide test when identifying the ions in an unknown solution

A

1 - pour about 1cm depth of each of the labelled sodium solutions into the five test tubs in the rack

2 - add a few drops of dilute nitric acid to each solution, then add 1cm depth of silver nitrate solution

2 - record observations in a table

40
Q

what observation will be made if halide ions are present during the halide test

A

chloride = white

bromide = cream

iodide = yellow

41
Q

calcium + sodium hydroxide

A

white precipitate

42
Q

aluminium + sodium hydroxide

A

white redissolved precipitate

43
Q

magnesium + white precipitate

A

white precipitate

44
Q

advantages of using instrumental methods

A

accurate

rapid

sensitive

45
Q

method of flame emission spectroscopy

A

1 - sample injected into flame

2 - light of specific wave lengths emitted

3 - the light emitted is analysed by splitting it into its component colours

46
Q

disadvantages of flame emission spectroscopy

A

destructive - the sample being tested is burned

only identifies the prescense of elements not compounds

chemistry (11 decks)

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