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chemistry all note flashcards - 3rd And 4th > 4.6 - Chemical analysis > Flashcards

4.6 - Chemical analysis Flashcards

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1
Q

what is the test for hydrogen (H2)

A

squeaky pop test

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2
Q

what is the method of the test for hydrogen

A
  1. collect a sample of gas in a test tube
  2. attempt to ignite the gas using a lit splint
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3
Q

what is the result of the test for hydrogen

A

squeaky pop sound

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4
Q

what is the chemical reaction that takes place in the test for hydrogen

A

the combustion of H2 to from H2O

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5
Q

what is the equation for the test for hydrogen

A

2H2 (g) + O2 (g) –> 2H2O (g)

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6
Q

what causes the pop sound in the hydrogen test

A

the hot gas rushing out of the test tube

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7
Q

what is the test for oxygen (O2)

A

glowing splint test

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8
Q

what is the method of the test for oxygen

A
  1. collect a sample of gas in a test tube
  2. place a glowing splint into the test tube
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9
Q

what is the result of the test for oxygen

A

the splint relights

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10
Q

what is the chemical reaction that takes place in the test for oxygen

A

combustion of the wood in the splint

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11
Q

what causes the splint to relight in the test for oxygen

A

pure O2 is more concentrated than the O2 in normal air, meaning the wood in the splint combusts faster

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12
Q

what is the test for the presence of water (H2O)

A

copper sulfate test

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13
Q

what is the method of the test for the presence of H2O

A

add anhydrous copper sulfate (CuSO4)

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14
Q

what is the result of the test for the presence of H2O

A

it changes colour from white to blue

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15
Q

what is the test for the purity of H2O

A

measure its boiling point and compare it to 100 degrees C

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16
Q

what is the method of the test for the purity of H2O

A

heat it and measure its boiling point

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17
Q

what is the result of the test for the purity of H2O

A

the closer it is to 100 degrees C, the more pure it is

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18
Q

what is the test for carbon dioxide (CO2)

A

limewater test

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19
Q

what is the method of the test for carbon dioxide

A

bubble a sample of gas through limewater

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20
Q

what is the result of the test for carbon dioxide

A

a white precipitate forms - it turns cloudy

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21
Q

what type of solution is limewater

A

saturated calcium hydroxide solution Ca(OH)2

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22
Q

what is the precipitate that forms when limewater reacts with CO2

A

a white precipitate of calcium carbonate (CaCO3)

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23
Q

what is the equation for the test for carbon dioxide

A

Ca(OH)2 (aq) +CO2 (g) –> CaCO3 (s) + H2O (l)

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24
Q

what is the test for chlorine (Cl2)

A

damp blue litmus test

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25
Q

what is the method of the test for chlorine

A

place damp blue litmus paper in a sample of gas

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26
Q

what is the result of the test for chlorine

A

it turns white (bleaches)

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27
Q

what reaction occurs in the test for chlorine

A

Cl2 is a good bleaching agent, so it easily removes colour from other substances
in this test, it dissolves into the dampness (H2O) and removes colour from blue litmus

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28
Q

what is the test for ammonia (NH3)

A

damp red litmus test

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29
Q

what is the method of the test for ammonia

A

place damp red litmus paper in a sample of gas

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30
Q

what is the result of the test for ammonia

A

it turns blue

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31
Q

what reaction occurs in the test for ammonia

A

the NH3 reacts with the dampness (H2O) to form OH- ions
the NH3 acts as a base by accepting H+ ions from the H2O
the OH- ions are what’s left after H2O has lost H+, and they are alkaline so the litmus turns blue

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32
Q

what is the equation of the test for ammonia

A

NH3 (g) + H2O (l) –> NH4+ (aq) + OH- (aq)

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33
Q

what are the cations for chemical tests

A

Li+, Na+, K+, Ca 2+, Cu 2+, Fe 2+, Fe 3+, NH4+

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34
Q

what are cations

A

positive ions

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35
Q

what do many metal cations cause a non-luminous (blue) bunsen flame to do

A

change colour

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36
Q

how do you conduct a flame test

A
  1. dip a piece of nichrome/ platinum wire into hydrochloric acid - these wires don’t colour the flame and the acid cleans the wire
  2. dip the wire into a sample of solid or solution - this causes some of the sample to stick onto the wire
  3. place the tip of the wire into a non-luminous bunsen flame
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37
Q

what is the metal cation if the flame colour is red

A

Li+

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38
Q

what is the metal cation if the flame colour is yellow

A

Na+

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39
Q

what is the metal cation if the flame colour is lilac

A

K+

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39
Q

what is the metal cation if the flame colour is orange-red

A

Ca 2+

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40
Q

what is the metal cation if the flame colour is blue-green

A

Cu 2+

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41
Q

what is the flame colour if the metal cation is Li+

A

red

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42
Q

what is the flame colour if the metal cation is Na+

A

yellow

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43
Q

what is the flame colour if the metal cation is K+

A

lilac

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44
Q

what is the flame colour if the metal cation is Ca 2+

A

orange-red

45
Q

what is the flame colour if the metal cation is Cu 2+

A

blue-green

46
Q

what is sodium hydroxide (NaOH) used to test for - forms ppt

A

Cu 2+, Fe 2+, Fe 3+

47
Q

if Cu 2+, Fe 2+ or Fe 3+ is present in a sodium hydroxide test what forms

A

a metal hydroxide precipitate

48
Q

how do you conduct a sodium hydroxide test

A
  1. dissolve the sample in water
  2. add a few drops of NaOH (aq)
49
Q

if the precipitate colour is blue in a sodium hydroxide test what is the metal cation

A

Cu 2+

50
Q

if the precipitate colour is green in a sodium hydroxide test what is the metal cation

A

Fe 2+

51
Q

if the precipitate colour is brown in a sodium hydroxide test what is the metal cation

A

Fe 3+

52
Q

if the metal cation is Cu 2+ what is the precipitate colour

A

blue

53
Q

if the metal cation is Fe 2+ what is the precipitate colour

A

green

54
Q

if the metal cation is Fe 3+ what is the precipitate colour

A

brown

55
Q

if the precipitate colour is blue what is the precipitate formula

A

Cu(OH)2

56
Q

if the precipitate colour is green what is the precipitate formula

A

Fe(OH)2

57
Q

if the precipitate colour is brown what is the precipitate formula

A

Fe(OH)3

58
Q

if the precipitate formula is Cu(OH)2 what is the precipitate colour

A

blue

59
Q

if the precipitate formula is Fe(OH)2 what is the precipitate colour

A

green

60
Q

if the precipitate formula is Fe(OH)3 what is the precipitate colour

A

brown

61
Q

if the metal cation is Cu 2+ what is the precipitate formula

A

Cu(OH)2

62
Q

if the metal cation is Fe 2+ what is the precipitate formula

A

Fe(OH)2

63
Q

if the metal cation is Fe 3+ what is the precipitate formula

A

Fe(OH)3

64
Q

if the precipitate formula is Cu(OH)2 what is the metal cation

A

Cu 2+

65
Q

if the precipitate formula is Fe(OH)2 what is the metal cation

A

Fe 2+

66
Q

if the precipitate formula is Fe(OH)3 what is the metal cation

A

Fe 3+

67
Q

what two types of equations can you write for the reaction in a sodium hydroxide test

A

fully balanced equation
ionic equation

68
Q

what would a fully balanced equation for the reaction between NaOH and CuCl2 look like

A

CuCl2 (aq) + 2NaOH(aq) –> Cu(OH)2 (s) + 2NaCl (aq)
sample blue ppt
containing
Cu 2+

69
Q

what would an ionic equation for the reaction between NaOH and Cu 2+ look like

A

Cu 2+ (aq) + 2OH- (aq) –> Cu(OH)2 (s)

70
Q

what sodium hydroxide (NaOH) used to test for - gas forms

A

ammonium (NH4+) ions

71
Q

if ammonium ions are present in a sodium hydroxide test what forms

A

a gas which is then tested to see if it is ammonia (NH3)

72
Q

how do you conduct an ammonium test

A
  1. dissolve the sample in water
  2. add some NaOH (aq) and warm it
  3. test the gas evolved with damp red litmus paper (the ammonia test)
73
Q

what is the result if NH4+ ions are present in the original sample in the ammonium test

A

the litmus paper will turn blue

74
Q

how does the ammonium test work

A

the NH4+ from the sample and OH- ions from the NaOH react to produce NH3 (g)

75
Q

what is the equation for the reaction for the ammonium test

A

NH4+ (aq) + OH- (aq) –> NH3 (g) + H2O (l)
sample test with
containing damp red
NH4+ litmus paper

76
Q

what are anions

A

negative ions

77
Q

what are the anions for chemical tests

A

Cl-, Br-, I-, CO3 2-, SO4 2-

78
Q

what are the halide ions

A

Cl-, Br-, I-

79
Q

what test is used to test the halide ions - Cl-, Br-, I-

A

silver nitrate test

80
Q

how do you conduct the silver nitrate test

A
  1. dissolve the sample in water
  2. add nitric acid (HNO3)
  3. add silver nitrate (AgNO3) solution
81
Q

if Cl-, Br- or I- ions are present in the silver nitrate test what is formed

A

a precipitate with the Ag+ ions from the AgNO3

82
Q

if the precipitate colour is white what is the halide ion

A

Cl-

83
Q

if the precipitate colour is cream what is the halide ion

A

Br-

84
Q

if the precipitate colour is yellow what is the halide ion

A

I-

85
Q

if the halide ion is Cl- what is the precipitate colour

A

white

86
Q

if the halide ion is Br- what is the precipitate colour

A

cream

87
Q

if the halide ion is I- what is the precipitate colour

A

yellow

88
Q

if the precipitate colour is white what is the precipitate formula

A

AgCl

89
Q

if the precipitate colour is cream what is the precipitate formula

A

AgBr

90
Q

if the precipitate colour is yellow what is the precipitate formula

A

AgI

91
Q

if the precipitate formula is AgCl what is the precipitate colour

A

white

92
Q

if the precipitate formula is AgBr what is the precipitate colour

A

cream

93
Q

if the precipitate formula is AgI what is the precipitate colour

A

yellow

94
Q

if the halide ion is Cl- what is the precipitate formula

A

AgCl

95
Q

if the halide ion is Br- what is the precipitate formula

A

AgBr

96
Q

if the halide ion is I- what is the precipitate formula

A

AgI

97
Q

if the precipitate formula is AgCl what is the halide ion

A

Cl-

98
Q

if the precipitate formula is AgBr what is the halide ion

A

Br-

99
Q

if the precipitate formula is AgI what is the halide ion

A

I-

100
Q

what does the equation for the formation of the precipitate AgCl look like

A

Ag+ (aq) + Cl- (aq) –> AgCl (s)

101
Q

why is it important to add the HNO3 in the test for halides

A

because Ag+ ions also form precipitates with other anions (OH- and CO3 2-) the HNO3 reacts with those anions, preventing false positives

102
Q

how do you conduct the test for carbonate (CO3 2-) ions

A
  1. add hydrochloric acid (HCl) - look for effervescence
  2. if there is effervescence, bubble the gas through limewater
103
Q

what is the result if CO3 2- ions are present in the sample in the test for carbonates

A

the gas evolved turns the limewater cloudy

104
Q

what would the reaction equation look like using calcium carbonate (CaCO3) as the sample

A

CaCO3 (s) + 2HCl (aq) –> CaCl2 (aq) + H2O (l) + CO2 (g)
sample test using
containing limewater
CO3 2-

105
Q

why is it important to confirm the gas evolved is CO2 using limewater

A

acids also evolve a gas when they react with some other things - checking that the gas is CO2 prevents false positives

106
Q

how do you conduct the test for sulfate (SO4 2-) ions

A
  1. add hydrochloric acid (HCl) - look for effervescence
  2. if there is no effervescence, add barium chloride (BaCl2) solution
107
Q

what is the result of the sulfate test if SO4 2- ions are present

A

it will form a white precipitate with the Ba 2+ ions from the BaCl2

108
Q

what would an equation for the formation of the white precipitate (BaSO4) look like

A

Ba 2+ (aq) + SO4 2- (aq) –> BaSO4 (s)

109
Q

why is it important to add the HCl when testing for sulfates

A

because carbonate (CO3 2-) ions also form a white precipitate with Ba 2+ ions - prevents false positives

chemistry all note flashcards - 3rd And 4th (13 decks)

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