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Table 1 Common cations and anions: Positive ions (Cations) Charge Name Hydrogen ion Lithium ion Sodium ion +1 Potassium ion Silver ion



Formula H+ Li+ Na+ K+ Ag+



Negative ions (Anions) Name Hydroxide ion Fluoride ion Chloride ion Bromide ion Iodide ion Hydride ion Nitrate ion

Formula OHFClBrIHNO3-

Ammonium ion


Magnesium ion Calcium ion Lead (II) ion Copper (II) ion

Mg2+ Ca2+ Pb2+ Cu2+

Nitrite ion Hydrogencarbonate ion Hydrogensulphate ion Permanganate ion


Zinc ion Iron (II) ion Mercury (II) ion Manganese (II) ion Cobalt (II) ion Nickel (II) ion

Zn2+ Fe2+ Hg2+ Mn2+ Co2+ Ni2+

Oxide ion Sulphide ion Sulphite ion Sulphate ion Chromate ion Dichromate ion


Aluminum ion


Carbonate ion


Iron (III) ion Chromium (III) ion

Fe3+ Cr3+

Nitride ion Phosphide ion Phosphate ion




-ide = simple anion; -ite = polyatomic anion with less O atoms -ate = polyatomic anion with more O atoms Table 2 Colour of ions in aqueous solutions: Ion Color Ion Color Copper (II) Cobalt (II) Blue Pink Cu2+ Co2+ Nickel (II) Chromate Green Yellow Ni2+ CrO42Chromium (III) Dichromate Green Orange Cr3+ Cr2O72Iron (III) Permanganate Yellow Purple Fe3+ MnO4Pale pink Iron (II) Manganese (II) Green / 2+ 2+ Fe Mn colorless Table 4 Solubility of ionic compounds in water Compound of… Solubility in water + Potassium K All are soluble Sodium Na+ All are soluble + Ammonium NH4 All are soluble Nitrate NO3 All are soluble Hydrogencarbonate All are soluble HCO3All are soluble Halide Xexcept AgX and PbX2 All are soluble Sulphate SO42except CaSO4, PbSO4 and BaSO4 All are insoluble Carbonate CO32except Na2CO3, K2CO3 and (NH4)2CO3 All are insoluble except K2O, Na2O, KOH Oxide O2-and and NaOH. hydroxide OH CaO and Ca(OH)2 are slightly soluble in water

Table 3 Flame colors of some common metal ions: Metal ion Sodium Potassium Calcium Copper (II)

Flame color Golden yellow flame Lilac flame Brick-red Bluish-green

Table 5 Solubility in water, colour and smell of gases Solubility Gas Color Smell in water Ammonia NH3 Soluble Colorless Pungent smell Sulphur dioxide Soluble Colorless Pungent smell SO2 Nitrogen dioxide Soluble Brown Pungent smell NO2 Pungent smell / Greenish Chlorine Cl2 Soluble swimming pool yellow smell Hydrogen chloride Soluble Colorless Acidic smell HCl Hydrogen Soluble Colorless Bad egg smell sulphide H2S Slightly Oxygen O2 Colorless Odorless soluble Carbon dioxide Slightly Colorless Odorless CO2 soluble Hydrogen H2 Insoluble Colorless Odorless Nitrogen N2 Insoluble Colorless Odorless Carbon Insoluble Colorless Odorless monoxide CO

Table 6 Test for gases:

Positive result Chemical equation (if any)


How to test

Hydrogen H2

Burning splint

Give a ‘pop’ sound 2H2(g) + O2(g)  2H2O(l)

Oxygen O2

Glowing splint

Glowing splint relights

Chlorine Cl2

Wet blue litmus paper

Carbon monoxide CO

Citrated blood

Carbon dioxide CO2

Lime water

Water vapor H2O

Anhydrous cobalt(II) chloride paper Anhydrous copper(II) sulphate powder

Blood turns from dark red to cherry red Limewater turns from colorless to milky Ca(OH)2(aq) + CO2(g)  CaCO3(s) + H2O(l)

Wet red litmus paper Ammonia NH3

Place near concentrated hydrochloric acid

Sulphur dioxide SO2

Paper turns from blue to pink Powder turns from white to blue Red litmus paper turns blue NH3(g) + H2O(l) NH4+(aq) + OH-(aq) A dense white fume, NH4Cl(s) is formed NH3(g) + HCl(g)  NH4Cl

(bubble into) Acidified potassium dichromate solution

Dichromate solution turns from orange to green 3SO2(g) + Cr2O72-(aq) + 2H+(aq)  3SO42-(aq) + 2Cr3+(aq) + H2O(l)

(bubble into) Acidified potassium permanganate solution

Permangate solution turns from purple to colorless 5SO2(g) + 2MnO4-(aq) + 2H2O(l)  5SO42-(aq) + 2Mn2+(aq) + 4H+(aq)

(bubble into) Bromine water Table 7 Test for cations: Cation

Blue litmus paper turns red and then white Cl2(g) + H2O(l) HCl(aq) + HOCl(aq) OCl-(aq) + dye  (dye+O) + Cl-(aq)

How to test

Potassium ion K+ Sodium ion Na+

Bromine water turns from yellowish brown to colorless

SO2(g) + Br2(g) + 2H2O(l)  SO42-(aq) + 2Br-(aq) + 4H+(aq)

Observation Chemical equation and remarks No observable change

Calcium ion Ca2+

+ NaOH(aq): White precipitate is formed Ca2+(aq) + 2OH-(aq)  Ca(OH)2(s)

Magnesium ion Mg2+

White precipitate is formed Mg2+(aq) + 2OH-(aq)  Mg(OH)2(s)

Aluminum ion Al

Lead(II) ion Pb

White precipitate is formed Al3+(aq) + 3OH-(aq)  Al(OH)3(s) White precipitate re-dissolves in excess sodium hydroxide solution to give a colorless solution



Zinc ion Zn2+

Copper (II) ion Cu


Add sodium hydroxide or ammonia solution

White precipitate is formed Pb2+(aq) + 2OH-(aq)  Pb(OH)2(s) White precipitate re-dissolves in excess sodium hydroxide solution to give a colorless solution White precipitate is formed Zn2+(aq) + 2OH-(aq)  Zn(OH)2(s) White precipitate re-dissolves in excess sodium hydroxide / ammonia solution to give a colorless solution Blue precipitate is formed Cu2+(aq) + 2OH-(aq)  Cu(OH)2(s) Blue precipitate re-dissolves in excess ammonia solution to give a deep blue solution

Iron (II) ion Fe2+

Dirty-green precipitate is formed Fe2+(aq) + 2OH-(aq)  Fe(OH)2(s)

Iron (III) ion Fe3+

Brown precipitate is formed Fe3+(aq) + 3OH-(aq)  Fe(OH)3(s)

Re-dissolve in excess NaOH(aq): Al(OH)3(s), Pb(OH)2(s) and Zn(OH)2(s) ‘又叻又醒就攞A’ Re-dissolve in excess NH3(aq): Zn(OH)2(s), Cu(OH)2(s) and Ag2O(s) ‘少少醒就攞C’ Warm with A pungent gas which turns wet red litmus paper blue is produced Ammonium ion NH4+ sodium hydroxide NH4+(aq) + OH-(aq)  NH3(g) + H2O(l) solution

Table 8 Test for anions:

Observation Chemical equation and remarks


How to test

Chloride ion Cl-

*Acidified silver nitrate solution

White precipitate is formed

Bromide ion Br-

*To prevent the formation of other insoluble solids like Ag2CO3

Pale yellow precipitate is formed

Iodide ion I-

Yellow precipitate is formed

Ag+(aq) + Cl-(aq)  AgCl(s) Ag+(aq) + Br-(aq)  AgBr(s) Ag+(aq) + I-(aq)  AgI(s)

Carbonate ion CO32Hydrogencarbonate ion HCO32-

Dilute acid

Gas bubbles produced which turns limewater milky XCO3(s) + 2H+(aq)  X2+(aq) + CO2(g) + H2O(l) HCO3-(aq) + H+(aq)  CO2(g) + H2O(l)

Hypochlorite ion OCl-

Add dilute acid and test the gas produced by a wet pH paper

A greenish yellow gas is produced which will t urn wet pH paper to red and then white OCl-(aq) + Cl-(aq) + 2H+(aq)  Cl2(g) + H2O(l) HCl(aq) + HOCl(aq) Cl2(g) + H2O(l) OCl-(aq) + dye  (dye+O) + Cl-(aq)

Acidified potassium dichromate solution Acidified potassium permanganate solution Sulphite ion SO32-

Bromine water Add dilute acid and then test the gas produced by acidified potassium dichromate solution

Table 9 Structures, particles and bonding

Dichromate solution turns from orange to green 3SO32-(aq) + Cr2O72-(aq) + 8H+(aq)  3SO42-(aq) + 2Cr3+(aq) + 4H2O(l) Permangate solution turns from purple to colorless 5SO32-(aq) + 2MnO4-(aq) + 6H+(aq)  5SO42-(aq) + 2Mn2+(aq) + 3H2O(l) Bromine water turns from yellowish brown to colorless

SO32-(aq) + Br2(aq) + H2O(l)  SO42-(aq) + 2Br-(aq) + 2H+(aq)

A pungent gas produced which turns dichromate solution from orange to green SO32-(aq) + 2H+(aq)  SO2(g) + H2O(l)

Table 10 Metal reactivity series / methods of metal extraction from its ores / reaction with oxygen, water and dilute acids MRS

Methods of extraction

Burns violently with a lilac flame 4K(s) + O2(g)  2K2O(s)


Burns violently with a golden yellow flame 4Na(s) + O2(g)  2Na2O(s)



Electrolysis of its molten ores





Heating with C (other possible reducing agent: H2(g), CO(g) and towngas)


Ag Au *

Burns with a brick-red flame 2Ca(s) + O2(g)  2CaO(s)

Reaction with water or steam Melts to a silvery ball Moves rapidly on the water surface Burns with a lilac flame Colourless solution is formed 2K(s) + 2H2O(l)  2KOH(aq) + H2(g)

Gas bubbles produced. Milky solution is formed. Ca(s) + 2H2O(l)  Ca(OH)2(aq) + H2(g)

Burns with a bright white flame 2Mg(s) + O2(g)  2MgO(s)

Glows in steam White powder is formed Mg(s) + H2O(g)  MgO(s) + H2(g)

White powder is formed 4Al(s) + 3O2(g)  2Al2O3(s)

React similarly as Mg with less vigor 2Al(s) + 3H2O(g)  Al2O3(s) + 3H2(g)

Powder (yellow when hot, white when cold) is formed. 2Zn(s) + O2(g)  2ZnO(s)

Reacts similarly as Al with less vigor Powder (yellow when hot, white when cold) is formed Zn(s) + H2O(g)  ZnO(s) + H2(g)

Iron powder burns with sparks Black solid is formed 3Fe(s) + 2O2(g)  Fe3O4 (a mixture of FeO and Fe2O3)

Reacts similarly as Zn with less vigor Black powder is formed 3Fe(s) + 4H2O(g)  Fe3O4(s) + 4H2(g)

Heating alone Exists as free element

Black powder is formed 2Cu(s) + O2(g)  2CuO(s) Red powder is formed 2Hg(l) + O2(g)  2HgO(s)

Reaction with dilute acids (HCl and H2SO4)

Explosive reaction.

Similar to K, but burns with a golden yellow flame 2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)

Powder (orange when hot, yellow when cold) is formed 2Pb(s) + O2(g)  2PbO(s)



Reaction with oxygen

Sink in acid Dissolves to give a colorless solution Gas bubbles are evolved Ca(s) + 2HCl(aq) CaCl2(aq) + H2(g) *Ca(s) + H2SO4(aq)  no apparent reaction Reacts similarly as calcium with less vigor Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g) Mg(s) + H2SO4(aq)  MgSO4(aq) + H2(g) Reacts similarly as Mg with less vigor 2Al(s) + 6HCl(aq) 2AlCl3(aq) + 3H2(g) 2Al(s) + 3H2SO4(aq)  Al2(SO4)3(aq) + 3H2(g) React similarly as Al with less vigor Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g) Zn(s) + H2SO4(aq)  ZnSO4(aq) + H2(g) React similarly as Zn with less vigor A green solution is formed Fe(s) + 2HCl(aq) FeCl2(aq) + H2(g) Fe(s) + H2SO4(aq)  FeSO4(aq) + H2(g) *Pb(s) + HCl(aq)  no apparent reaction *Pb(s) + H2SO4(aq)  no apparent reaction

No reaction No reaction

No reaction

Due to insoluble layer (CaSO4(s), PbCl2(s) and PbSO4(s)) is formed between metal and acid, which prevents further reaction.

Table 11 Metal reactivity series (M.R.S.) & Electrochemical series (E.C.S) E.C.S. M.R.S. Cations Anions OHK K+ INa Ca2+ + BrCa Na 2+ ClMg Mg 3+ NO3Al Al 2+ SO42Zn Zn 2+ Fe Fe Pb Pb2+ Cu H+ Hg Cu2+ Ag Hg2+ Au Ag+

Table 12 Reaction between metal and acids:

HCl(aq) H2SO4(aq) HNO3(aq)

Table 13 Test for carbon compounds: Functional group

How to test

Very dilute



> Cu

> Cu

> Cu

 H2(g)

 H2(g)

 H2(g)

> Cu

> Cu

≥ Cu

 H2(g)

 H2(g)

 SO2(g)

> Cu

≥ Cu

≥ Cu

 H2(g)

 NO(g)

 NO2(g)

Observation Chemical equation and remarks Bromine will be decolorized from red-orange to colorless rapidly.

Add bromine in organic solvent in the dark Alkene C=C Add acidified potassium permanganate solution

Permanganate turns from purple to colorless

Dichromate turns from orange to green For 1o and 2o alkanol only:

Alkanol -OH

1o alkanol:

Warm with acidified potassium dichromate solution 2o alkanol: Warm with alkanoic acid and a few drops of conc. H2SO4

3o alkanol: no reaction

Fruity smell produced

Orange precipitate (2,4-dintrophenylhydrazone) is formed. Carbonyl compound (aldehyde and ketone)



Tollen’s reagent (Silver nitrate solution in excess ammonia solution)

Alkanoic acid –COOH


Silver mirror is formed on the surface of test tube CH3CHO + 2[Ag(NH3)2]+ + 3OH CH3COO- + 2Ag + 4NH3 + 2H2O

Carbonate solution / hydrogencarbonate solution

Gas bubbles produced which turns limewater milky. 2CH3COOH + Na2CO3  2CH3COO-Na+ + H2O + CO2

Warm with alkanol and a few drops of conc. H2SO4

Fruity smell produced


Gaseous amines: smell of ammonia Liquid amines: fishy smell Fruity smell



Table 14 Reagents and conditions for organic reactions

Table 15 Inter-conversion between different functional groups

Table 16 acid-base properties of the oxides of elements from Na to Cl

Table 17 Fossil fuels fractions

Table 19 Le Chatelier’s principle

Table 18 Strength and basicity of acid

Table 20 Common oxidizing agents and reducing agents

Table 21 Roles of Conc. H2SO4(l)  Conc. H2SO4(l) as dehydrating agent

Add into glucose (C6H12O6) Conc. H2SO4(l)

Observation: Glucose turns black and white fumes form  Conc. H2SO4(l) as oxidising agent

React with Cu(s) Observation: Cu dissolves. / Solution turns blue. / Colorless gas produced.  Conc. H2SO4(l) as an acid

React with sodium carbonate Observation: Colorless gas produced.

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DSE Chemistry (table of information)  

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DSE Chemistry (table of information)

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