Qualitative analysis Flashcards
1
Q
What reagents are used to identify cations?
A
- sodium hydroxide
- aq ammonia
2
Q
What is the effect of aqueous sodium hydroxide on calcium?
A
- white ppt
- insoluble in excess
3
Q
What is the effect of aqueous ammonia on calcium?
A
- no ppt
- or very slight white ppt
4
Q
What is the effect of aqueous sodium hydroxide on zinc?
A
- white ppt
- soluble in excess (gives colourless solution)
5
Q
What is the effect of aqueous ammonia on zinc?
A
- white ppt
- soluble in excess (gives a colourless solution)
6
Q
What is the effect of aqueous sodium hydroxide on aluminium?
A
- white ppt
- soluble in excess (gives colourless solution)
7
Q
What is the effect of aqueous ammonia on aluminium?
A
- white ppt
- insoluble in excess
8
Q
What is the effect of aqueous sodium hydroxide on lead?
A
- white ppt
- soluble in excess (gives colourless solution)
9
Q
What is the effect of aqueous ammonia on lead?
A
- white ppt
- insoluble in excess
10
Q
What is the effect of aqueous sodium hydroxide on copper (ll)?
A
- light blue ppt
- insoluble in excess
11
Q
What is the effect of aqueous ammonia on copper (ll)?
A
- light blue ppt
- soluble in excess (gives a dark blue solution)
12
Q
What is the effect of aqueous sodium hydroxide on iron (ll)?
A
- green ppt
- insoluble in excess
13
Q
What is the effect of aqueous ammonia on iron (ll)?
A
- green ppt
- insoluble in excess
14
Q
What is the effect of aqueous sodium hydroxide on iron (lll)?
A
- red-brown ppt
- insoluble in excess
15
Q
What is the effect of aqueous ammonia on iron (lll)?
A
- red-brown ppt
- insoluble in excess
16
Q
What is the effect of aqueous sodium hydroxide on ammonium?
A
- ammonia produced upon warming
17
Q
How does one differentiate between lead and aluminum ions?
A
- add potassium iodide
- in lead ion is present, bright yellow ppt of lead (ll) iodide will be observed
- if aluminium is present, no visible change occurs
18
Q
What is another way to differentiate between lead and aluminium ions other than adding potassium iodide?
A
- add dilute HCl
- if lead ion is present, a white ppt or PbCl2 will be observed
- if aluminium ion is present, no visible change occurs
19
Q
How does one identify a carbonate ion?
A
- add dilute acid
- if carbonate ion is present, effervescence will be observed
- gas forms white ppt in limewater
- carbon dioxide is produced
20
Q
How does one identify a chloride ion?
A
- acidify with dilute nitric acid
- then add aq silver nitrate
- if chloride ion is present, a white ppt is formed (silver chloride)
21
Q
How does one identify an iodide ion? (1 of 2 ways)
A
- acidify with dilute nitric acid
- add aq silver nitrate
- if iodide ion is present, a yellow ppt is formed
22
Q
How does one identify an iodide ion (2 of 2 ways)
A
- acidify with dilute nitric acid
- add aq lead (ll) nitrate
- if iodide ion is present,
a bright yellow ppt is formed
23
Q
How does one identify a nitrate ion?
A
- add aq sodium hydroxide
- then aluminium foil
- warm
- if nitrate ion is present, effervescence is observed
- moist red litmus turns blue (ammonia produced)
24
Q
How does one identify a sulfate ion?
A
- acidify with dilute nitric acid
- add aq barium nitrate
- if sulfate ion is present, white ppt is formed
25
How does one test for ammonia?
- place a damp piece of red litmus paper near the mouth of the test tube containing the gas
- ammonia gas turns damp red litmus paper blue
26
How does one describe ammonia?
- colourless
- pungent gas
27
How does one test for carbon dioxide?
- bubble the gas into lime water
- carbon dioxide gas forms a white ppt of CaCO3 with limewater
28
How does one describe carbon dioxide?
- colourless
- odorless gas
29
How does one test for chlorine gas?
- place a damp piece of blue litmus near the mouth of the test tube containing the gas
- chlorine gas turns damp blue litmus paper red
- it then bleaches damp litmus paper
30
How does one describe chlorine gas?
- greenish-yellow
- pungent gas
31
How does one test for oxygen?
- insert a glowing splint into the mouth of the test tube containing the gas
- oxygen gas relights a glowing splint
32
how does one describe oxygen?
- colourless
- odorless gas
33
How does one test for water vapour?
- place cobalt (ll) chloride paper near the mouth of the test tube containing the vapour
- if vapour turns blue cobalt (ll) chloride paper pink, water vapour is present
34
How does one test for liquid water?
- the vapour must be cooled and condensed into liquid
- add a few drops of liquid to anhydrous copper (ll) sulfate
- if the white anhydrous copper (ll) sulfate turns blue, water is present
35
What is decomposition?
- when a substance breaks down into simpler substances
36
What does ammonium chloride form when decomposed?
- ammonia gas
- hydrogen chloride gas
37
Can ammonia gas and hydrogen chloride gas recombine to form ammonium chloride?
- yes
- it is a reversible reaction
38
What happens to hydrated salts when heated gently?
- they lose water of crystallization
- become anhydrous salts
- water of crystallization appears as colourless droplets of liquid on the upper part of test tube
39
What do some carbonates give when decomposed?
- metal oxide
- carbon dioxide
40
What is zinc oxide when hot and cold?
- yellow solid when hot
- white solid when cold
41
What are the colours of some common substances?
- K, Na, Ca, Zn, Fe: silvery (polished) / grey (powder)
- Cu: reddish brown or brown
42
What colour are K2O, Na2O and CaO?
- white
43
What colour is ZnO?
- yellow when hot
- white when cold
44
What colour is FeO (iron(ll)) oxide?
- black
45
What colour is Fe2O3?
- reddish brown
46
What colour is CuO (copper (ll) oxide)?
- black solid
47
What colour is Cu2O (copper (ll) oxide) ?
- reddish brown solid
48
What colour is CuCO3 (copper (ll) carbonate)?
- green solid
49
What colour is CuSO4 (copper (ll) sulfate)?
- blue solid
50
What colour are KOH and NaOH?
- colourless
- soluble in water
51
Is Ca(OH)2 soluble in water?
- slightly
52
What colour is Zn(OH)2?
- white
- insoluble in water
53
What colour is Fe(OH)2?
- green/dirty green
- insoluble in water
54
What colour is Fe(OH)3?
- reddish brown ppt
- insoluble in water
55
What colour is Cu(OH)2?
- blue ppt
- insoluble in water
56
What colour are the salt solutions of K, Na, Ca and Zn?
- colourless
57
What colour is the salt solution of Fe (iron(ll))?
- green
58
What colour is the salt solution of Fe2 (iron(lll))?
- yellowish brown (lower conc.)
- reddish brown (higher conc.)
59
What colour is Cu (copper (ll)) salt solution?
- usually blue
60
What colour is CuCl2 (copper(ll) chloride) solution?
- bluish green
- green
61
What colour is carbon solid?
- black
62
What colour is fluorine gas?
- pale yellow (r.t.p)
63
What colour is bromine?
- reddish brown liquid (r.t.p)
- aq bromine and bromine gas are also reddish brown
64
What colour is iodine?
- black solid at r.t.p
- vapour is violet
- solution is yellowish-brown at lower conc. and reddish brown at higher conc.
65
What colour is nitrogen dioxide gas?
- reddish brown gas (r.t.p)
66
What colour is nitrogen monoxide gas?
- colourless (r.t.p)
- neutral gas
67
What colour is carbon monoxide gas?
- colourless (r.t.p)
- neutral gas
68
What colour is manganese(IV) oxide?
- black solid
69
What colour is potassium dichromate(VI)?
- orange solution
- green when reduced
70
What colour is universal indicator at different pH?
- red at pH 1
- green at pH 7
- violet/purple at pH 14
71
What colour is methyl orange at different pH?
- red/orange at pH<4
- yellow at pH>4
