4.6 - Chemical analysis Flashcards
(110 cards)
1
Q
what is the test for hydrogen (H2)
A
squeaky pop test
2
Q
what is the method of the test for hydrogen
A
- collect a sample of gas in a test tube
- attempt to ignite the gas using a lit splint
3
Q
what is the result of the test for hydrogen
A
squeaky pop sound
4
Q
what is the chemical reaction that takes place in the test for hydrogen
A
the combustion of H2 to from H2O
5
Q
what is the equation for the test for hydrogen
A
2H2 (g) + O2 (g) –> 2H2O (g)
6
Q
what causes the pop sound in the hydrogen test
A
the hot gas rushing out of the test tube
7
Q
what is the test for oxygen (O2)
A
glowing splint test
8
Q
what is the method of the test for oxygen
A
- collect a sample of gas in a test tube
- place a glowing splint into the test tube
9
Q
what is the result of the test for oxygen
A
the splint relights
10
Q
what is the chemical reaction that takes place in the test for oxygen
A
combustion of the wood in the splint
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
12
Q
what is the test for the presence of water (H2O)
A
copper sulfate test
13
Q
what is the method of the test for the presence of H2O
A
add anhydrous copper sulfate (CuSO4)
14
Q
what is the result of the test for the presence of H2O
A
it changes colour from white to blue
15
Q
what is the test for the purity of H2O
A
measure its boiling point and compare it to 100 degrees C
16
Q
what is the method of the test for the purity of H2O
A
heat it and measure its boiling point
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
18
Q
what is the test for carbon dioxide (CO2)
A
limewater test
19
Q
what is the method of the test for carbon dioxide
A
bubble a sample of gas through limewater
20
Q
what is the result of the test for carbon dioxide
A
a white precipitate forms - it turns cloudy
21
Q
what type of solution is limewater
A
saturated calcium hydroxide solution Ca(OH)2
22
Q
what is the precipitate that forms when limewater reacts with CO2
A
a white precipitate of calcium carbonate (CaCO3)
23
Q
what is the equation for the test for carbon dioxide
A
Ca(OH)2 (aq) +CO2 (g) –> CaCO3 (s) + H2O (l)
24
Q
what is the test for chlorine (Cl2)
A
damp blue litmus test
25
what is the method of the test for chlorine
place damp blue litmus paper in a sample of gas
26
what is the result of the test for chlorine
it turns white (bleaches)
27
what reaction occurs in the test for chlorine
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
28
what is the test for ammonia (NH3)
damp red litmus test
29
what is the method of the test for ammonia
place damp red litmus paper in a sample of gas
30
what is the result of the test for ammonia
it turns blue
31
what reaction occurs in the test for ammonia
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
32
what is the equation of the test for ammonia
NH3 (g) + H2O (l) --> NH4+ (aq) + OH- (aq)
33
what are the cations for chemical tests
Li+, Na+, K+, Ca 2+, Cu 2+, Fe 2+, Fe 3+, NH4+
34
what are cations
positive ions
35
what do many metal cations cause a non-luminous (blue) bunsen flame to do
change colour
36
how do you conduct a flame test
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
37
what is the metal cation if the flame colour is red
Li+
38
what is the metal cation if the flame colour is yellow
Na+
39
what is the metal cation if the flame colour is lilac
K+
39
what is the metal cation if the flame colour is orange-red
Ca 2+
40
what is the metal cation if the flame colour is blue-green
Cu 2+
41
what is the flame colour if the metal cation is Li+
red
42
what is the flame colour if the metal cation is Na+
yellow
43
what is the flame colour if the metal cation is K+
lilac
44
what is the flame colour if the metal cation is Ca 2+
orange-red
45
what is the flame colour if the metal cation is Cu 2+
blue-green
46
what is sodium hydroxide (NaOH) used to test for - forms ppt
Cu 2+, Fe 2+, Fe 3+
47
if Cu 2+, Fe 2+ or Fe 3+ is present in a sodium hydroxide test what forms
a metal hydroxide precipitate
48
how do you conduct a sodium hydroxide test
1. dissolve the sample in water
2. add a few drops of NaOH (aq)
49
if the precipitate colour is blue in a sodium hydroxide test what is the metal cation
Cu 2+
50
if the precipitate colour is green in a sodium hydroxide test what is the metal cation
Fe 2+
51
if the precipitate colour is brown in a sodium hydroxide test what is the metal cation
Fe 3+
52
if the metal cation is Cu 2+ what is the precipitate colour
blue
53
if the metal cation is Fe 2+ what is the precipitate colour
green
54
if the metal cation is Fe 3+ what is the precipitate colour
brown
55
if the precipitate colour is blue what is the precipitate formula
Cu(OH)2
56
if the precipitate colour is green what is the precipitate formula
Fe(OH)2
57
if the precipitate colour is brown what is the precipitate formula
Fe(OH)3
58
if the precipitate formula is Cu(OH)2 what is the precipitate colour
blue
59
if the precipitate formula is Fe(OH)2 what is the precipitate colour
green
60
if the precipitate formula is Fe(OH)3 what is the precipitate colour
brown
61
if the metal cation is Cu 2+ what is the precipitate formula
Cu(OH)2
62
if the metal cation is Fe 2+ what is the precipitate formula
Fe(OH)2
63
if the metal cation is Fe 3+ what is the precipitate formula
Fe(OH)3
64
if the precipitate formula is Cu(OH)2 what is the metal cation
Cu 2+
65
if the precipitate formula is Fe(OH)2 what is the metal cation
Fe 2+
66
if the precipitate formula is Fe(OH)3 what is the metal cation
Fe 3+
67
what two types of equations can you write for the reaction in a sodium hydroxide test
fully balanced equation
ionic equation
68
what would a fully balanced equation for the reaction between NaOH and CuCl2 look like
CuCl2 (aq) + 2NaOH(aq) --> Cu(OH)2 (s) + 2NaCl (aq)
sample blue ppt
containing
Cu 2+
69
what would an ionic equation for the reaction between NaOH and Cu 2+ look like
Cu 2+ (aq) + 2OH- (aq) --> Cu(OH)2 (s)
70
what sodium hydroxide (NaOH) used to test for - gas forms
ammonium (NH4+) ions
71
if ammonium ions are present in a sodium hydroxide test what forms
a gas which is then tested to see if it is ammonia (NH3)
72
how do you conduct an ammonium test
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
what is the result if NH4+ ions are present in the original sample in the ammonium test
the litmus paper will turn blue
74
how does the ammonium test work
the NH4+ from the sample and OH- ions from the NaOH react to produce NH3 (g)
75
what is the equation for the reaction for the ammonium test
NH4+ (aq) + OH- (aq) --> NH3 (g) + H2O (l)
sample test with
containing damp red
NH4+ litmus paper
76
what are anions
negative ions
77
what are the anions for chemical tests
Cl-, Br-, I-, CO3 2-, SO4 2-
78
what are the halide ions
Cl-, Br-, I-
79
what test is used to test the halide ions - Cl-, Br-, I-
silver nitrate test
80
how do you conduct the silver nitrate test
1. dissolve the sample in water
2. add nitric acid (HNO3)
3. add silver nitrate (AgNO3) solution
81
if Cl-, Br- or I- ions are present in the silver nitrate test what is formed
a precipitate with the Ag+ ions from the AgNO3
82
if the precipitate colour is white what is the halide ion
Cl-
83
if the precipitate colour is cream what is the halide ion
Br-
84
if the precipitate colour is yellow what is the halide ion
I-
85
if the halide ion is Cl- what is the precipitate colour
white
86
if the halide ion is Br- what is the precipitate colour
cream
87
if the halide ion is I- what is the precipitate colour
yellow
88
if the precipitate colour is white what is the precipitate formula
AgCl
89
if the precipitate colour is cream what is the precipitate formula
AgBr
90
if the precipitate colour is yellow what is the precipitate formula
AgI
91
if the precipitate formula is AgCl what is the precipitate colour
white
92
if the precipitate formula is AgBr what is the precipitate colour
cream
93
if the precipitate formula is AgI what is the precipitate colour
yellow
94
if the halide ion is Cl- what is the precipitate formula
AgCl
95
if the halide ion is Br- what is the precipitate formula
AgBr
96
if the halide ion is I- what is the precipitate formula
AgI
97
if the precipitate formula is AgCl what is the halide ion
Cl-
98
if the precipitate formula is AgBr what is the halide ion
Br-
99
if the precipitate formula is AgI what is the halide ion
I-
100
what does the equation for the formation of the precipitate AgCl look like
Ag+ (aq) + Cl- (aq) --> AgCl (s)
101
why is it important to add the HNO3 in the test for halides
because Ag+ ions also form precipitates with other anions (OH- and CO3 2-) the HNO3 reacts with those anions, preventing false positives
102
how do you conduct the test for carbonate (CO3 2-) ions
1. add hydrochloric acid (HCl) - look for effervescence
2. if there is effervescence, bubble the gas through limewater
103
what is the result if CO3 2- ions are present in the sample in the test for carbonates
the gas evolved turns the limewater cloudy
104
what would the reaction equation look like using calcium carbonate (CaCO3) as the sample
CaCO3 (s) + 2HCl (aq) --> CaCl2 (aq) + H2O (l) + CO2 (g)
sample test using
containing limewater
CO3 2-
105
why is it important to confirm the gas evolved is CO2 using limewater
acids also evolve a gas when they react with some other things - checking that the gas is CO2 prevents false positives
106
how do you conduct the test for sulfate (SO4 2-) ions
1. add hydrochloric acid (HCl) - look for effervescence
2. if there is no effervescence, add barium chloride (BaCl2) solution
107
what is the result of the sulfate test if SO4 2- ions are present
it will form a white precipitate with the Ba 2+ ions from the BaCl2
108
what would an equation for the formation of the white precipitate (BaSO4) look like
Ba 2+ (aq) + SO4 2- (aq) --> BaSO4 (s)
109
why is it important to add the HCl when testing for sulfates
because carbonate (CO3 2-) ions also form a white precipitate with Ba 2+ ions - prevents false positives
