QA Flashcards

1
Q

Possible white solid

A
  • compounds of group 1 and 2 metals
  • Zn2+/NH4+ compounds
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2
Q

Colourless solution

A

solutions of salts of group 1 and 2 metals, Zn2+/NH4+ salts, dilute acids/alkalis, hydrogen peroxide solution

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3
Q

Blue solid/solution

A

(Solution of) Hydrated Cu2+ salts

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4
Q

Green solid

A

Fe2+ salts(pale green), CuCO3

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5
Q

Green solution

A

Solution of Fe2+ salts(pale green)

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6
Q

Yellow solid

A

Fe3+ salts, AgI(pale yellow), PbI2(bright yellow), ZnO(hot)

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7
Q

Yellow solution

A

Dilute solution of Fe3+ salts

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8
Q

Brown/Red-brown solid

A

Fe2O3, Fe(OH)3, Cu(can be pink)

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9
Q

Brown solution

A

Concentrated solution of Fe3+ salts, i2(aqueous iodine)

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10
Q

Purple solid/solution

A

KMnO4

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11
Q

Grey solids

A

Metals except Cu and Au

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12
Q

Black solids

A

CuO, MnO2, I2(s), carbon powder

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13
Q

Solubility of (SO4)2- salts

A

All soluble except Ba, Ca, Pb, Ag(sparingly soluble)

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14
Q

Solubility of chloride salts

A

Soluble except Ag and Pb(except in hot water)

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15
Q

Solubility of carbonate salts

A

Insoluble except carbonates of group 1 metals and ammonium

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16
Q

Solubility of hydroxides and oxides

A

All insoluble except group 1 metals, Ba and Ca(slightly)

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17
Q

Test for hydrogen

A

Colourless, odourless gas evolved extinguishes lighted splint with ‘pop’ sound

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18
Q

Test for oxygen

A

Colourless, odourless gas relights a glowing splint

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19
Q

Test for carbon dioxide

A

Colourless, odourless gas evolved forms white precipitate with limewater

20
Q

Test for ammonia

A

Colourless, pungent gas turns damp red litmus paper blue

21
Q

Test for chlorine

A

Greenish-yellow, pungent gas turns damp blue litmus paper red, then bleaches it

22
Q

Explanation for test for chlorine(blue litmus turns red then bleach)

A

Chlorine reacts with water to form mixture of hydrochloric acid and hypochlorous acid. The acids turn damp blue litmus paper red. Hypochlorous acid bleaches the litmus paper

23
Q

Test for sulfur dioxide

A

(Use filter paper soaked with KMnO4) Colourless, pungent gas turns acidified potassium manganate(VII) from purple to colourless.

24
Q

Explanation for sulfur dioxide test

A

Sulfur dioxide is a reducing agent. It reduces purple manganate(VII) ion to colourless manganese(II) ion

25
Q

Test for ammonium

A

NaOH-> colourless, pungent gas evolved, (insert test for NH3)

26
Q

Test for Ca2+

A

NaOH -> white ppt, insoluble in excess
Ammonia -> NIL

27
Q

Test for Al3+

A

NaOH: white ppt, excess>colourless
NH3: white ppt, insoluble excess

28
Q

Test for Pb2+

A

NaOH: white ppt, excess>colourless
NH3: white ppt, insoluble excess

29
Q

Test for Zn2+

A

NaOH: white ppt, excess>colourless
NH3: white ppt, excess>colourless

30
Q

Test for Cu2+

A

NaOH: blue ppt, insoluble excess
NH3: blue ppt, excess>dark blue

31
Q

Test for Fe2+

A

NaOH: green ppt, insoluble excess
NH3: Green ppt, insoluble excess
^ppt turns red brown upon standing

32
Q

Test for Fe3+

A

NaOH: red-brown ppt, insoluble excess
NH3: red-brown ppt, insoluble excess

33
Q

Why no visible change if solution contains Na+ or K+

A

No reaction between aqueous NaOH or aqueous NH3 and solution containing Na+ or K+

34
Q

Why do some precipitates dissolve in excess aqueous sodium hydroxide

A

Ppts can react further with excess alkali to form complex salt that is soluble. White ppts, Al(OH), Pb(OH)2, Zn(OH)2 are amphoteric oxides and ppt further reacts with aqueous sodium hydroxide to form soluble complex salts

35
Q

Why do some precipitates dissolve in excess aqueous ammonia

A

Ppts can react further with excess alkali to form complex salt that is soluble. White ppt Zn(OH)2 and blue ppt Cu(OH)2 react with aqueous ammonia to form soluble complex salts

36
Q

Why ammonia gas produced when aqueous sodium hydroxide is added to a solution with NH4+?

A

Ammonium salts react with aqueous sodium hydroxide to form soluble salt, water and ammonia gas

37
Q

Why cant aqueous ammonia be used to test for NH4+

A

Upon heating, aqueous ammonia itself will produce ammonia gas. In this case, production of ammonia cannot be used to confirm presence of NH4+ in solution

38
Q

How to differentiate solutions containing Pb2+ and Al3+

A

Add aqueous solution containing iodide ions/chloride ions/ sulfate ions. Pb+I: bright yellow, Pb+Cl: white, Pb+SO4:white, Ag+any, no visible change

39
Q

Test for carbonate

A

Add dilute acids, observation and test for CO2

40
Q

Test for sulfate

A

Add dilute nitric acid followed by aqueous barium nitrate. White ppt is seen

41
Q

Test for chloride

A

Add dilute nitric acid followed by aqueous silver nitrate. White ppt is seen

42
Q

Test for iodide

A

Add dilute nitric acid followed by aqueous silver nitrate. Pale yellow ppt is seen

43
Q

Test for nitrate

A

Add aqueous sodium hydroxide followed by aluminium foil and warm. Test gas evolved with damp red litmus paper. (insert observation for ammonia)

44
Q

Purpose of adding dilute nitric acid before adding test reagent

A

To remove carbonate ion which may be present in unknown solution as carbonate ion will also react with test reagent to form precipitate

45
Q

Define thermal decomposition

A

A chemical process which heat is used to break down a single compound into two or more compounds or elements. A gas is usually produced in the process.