All Chemistry Formulas for O levels Chemistry by Ethan Wu
All Chemistry Formulas for O levels Chemistry by Ethan Wu
Hydrogen carbonate HCO3Hydride H-
Hydroxide OHCarbonate CO32-
Nitrate NO3Nitrite NO2Nitride N3Phosphate PO43Sulfate SO42Sulfite SO32Sulfide S2-
Ammonia NH3 Ammonium ion NH4+
Mole Concept One mole of any substance contains 6 X 1023 particles (Avogadro's number).
=
6 ? 1023
The molar mass of an element is the mass of one mole of atoms of the element.
= /
Percentage composition of compounds
=
?
100%
Empirical formula
Empirical formula of a compound is the simplest formula of the compound
Element
Element 1 Element 2
Mass/g or % by mass
Relative atomic mass
Number of moles
Mole ratio (divide by smallest number)
Simplest whole number
To find molecular formula
E.g. let molecular formula of ethane be (CH3)n
Relative mass of ethane from empirical formula = 15
=
Compiled by Ethan Wu Ying Tang
Molar volume of gases
3 . . .
=
24 000 3
Concentration of a solution (can be in terms of mol/dm3 or g/dm3)
/3
=
3
/3
=
3
= ? 100%
=
? 100%
Acids and Base Reactions Acids react with metals to form salt and hydrogen gas (except lead, insoluble salt) Initial reaction between lead and hydrochloric acid produce lead (II) chloride or lead (II) sulfate
which is insoluble. It will form a coating around metal and protect metal from further attack by acid. React with carbonates and hydrogen carbonates to form salt, water and carbon dioxide React with metal oxides and hydroxides to form salt and water
Alkalis heated with ammonium salts give out salt + water +ammonia
Solubility
Soluble salts
Insoluble salts
All sodium salts
All potassium salts
All ammonium salts
All nitrates
All chlorides
Silver chloride
Lead (II) chloride
All sulfates
Barium sulfate
Lead (II) sulfate
Calcium sulfate (sparingly soluble)
Sodium carbonate
Potassium carbonate
Ammonium carbonate
Hydroxide salts of Group I elements are soluble. Hydroxide salts of Group II elements (Ca, Sr, and Ba) are
slightly soluble. Hydroxide salts of transition metals and Al3+ are insoluble.
All oxides are insoluble except calcium (sparingly), barium and Group 1 metals but SO3 is soluble.
Compiled by Ethan Wu Ying Tang
Qualitative Analysis
Test for Cations
Cation
Sodium Hydroxide
Aqueous Ammonia
On adding a few On adding excess On adding a few On adding excess
drops
drops
Zinc ion Zn2+
White ppt
Ppt dissolves in White ppt
Ppt dissolves in
excess to form
excess to form
colourless
colourless
solution
solution
Aluminium ion AL3+ White ppt
Ppt dissolves in White ppt
Insoluble in
excess to form
excess
colourless
solution
Lead(II) ion PB2+
White ppt
Ppt dissolves in White ppt
Insoluble in
excess to form
excess
colourless
solution
Calcium ion Ca2+
White ppt
Insoluble in
No ppt
No ppt
excess
Copper (II) ion Cu2+ Light blue ppt Insoluble in
Light blue ppt
Ppt dissolves in
excess
excess to form
deep blue
solution
Iron (II) ion Fe2+
Green ppt
Insoluble in
Green ppt
Insoluble in
excess
excess
Iron (III) ion Fe3+
Reddish-brown Insoluble in
Reddish-brown Insoluble in
ppt
excess
ppt
excess
Ammonium ion
No ppt
No change
-
-
NH4+
On heating,
ammonia gas
give off
The ppt formed in each reaction is the hydroxide of the metal ion.
Test for Anions Anion Carbonate ion CO32-
Nitrate ion NO3-
Sulfate ion SO42-
Test
Add dilute hydrochloric acid Pass the gas given off into limewater
Add sodium hydroxide solution, then add a piece of aluminium foil. Warm the mixture. Test the gas given off with a piece of moist red litmus paper. Add dilute nitric acid, then add barium nitrate solution
Observations for positive test and inference Effervescence observed. Gas forms a white ppt with limewater. Carbon dioxide gas given off Effervescence observed The moist red litmus paper turns blue. Ammonia gas given off A white ppt of barium sulfate formed
Compiled by Ethan Wu Ying Tang
Chloride ion ClIodide ion I-
Add dilute nitric acid, then add silver nitrate solution Add dilute nitric acid, then add silver nitrate solution
A white ppt of silver chloride formed A yellow ppt of silver iodide formed
Identifying Gases Gas Hydrogen H2
Colour and Odour Colourless and odourless
Oxygen O2
Colourless and odourless
Carbon Dioxide CO2 Colourless and odourless
Chlorine Cl2
Greenish-yellow gas with a pungent smell
Sulfur Dioxide SO2 Colourless gas with a pungent smell
Ammonia NH3
Colourless gas with a pungent smell
Test Place a lighted splint at the mouth of the test tube Insert a glowing splint into the test tube Bubble gas through limewater
Place a piece of moist blue litmus paper at the mouth of the test tube Place a piece of filter paper soaked with acidified potassium manganate (VII) at the mouth of the test tube Place a piece of moist red litmus paper at the mouth of the test tube
Observations The light splint is extinguished with a `pop' sound The glowing splint is rekindled A white precipitate is formed The ppt dissolves upon further bubbling The moist blue litmus paper turns red and is then bleached
The purple acidified potassium manganate (VII) turns colourless
The moist red litmus paper turns blue
Redox Reaction Oxidising agents Bromine Chlorine Concentrated sulfuric acid Nitric acid Oxygen Ozone Potassium Manganate (VII) (KMnO4) Potassium Dichromate (VI) (Kr2Cr2O7)
Reducing agents Carbon Carbon Monoxide Hydrogen Hydrogen Sulfide Metals Potassium Iodide Sulfur Dioxide
Metal Potassium Sodium Calcium Magnesium
Reactivity series
Reaction with cold water
Reaction with steam
2K(s) + 2H2O(l) -> 2KOH(aq) +H2(g) React explosively
2Na(s) + 2H2O(l) -> 2NaOH(aq) +H2(g)
Ca(s) + 2H2O(l) -> Ca(OH)2(aq) + H2(g)
Mg(s) + 2H2O(l) -> Mg(OH)2(s) +H2(g) Mg(s) + H2O(g) -> MgO(s) + H2(g)
Compiled by Ethan Wu Ying Tang
Zinc
No reaction
Iron
No reaction (except rusting)
Lead Copper Silver
No reaction
Most reactive to least reactive K Na Ca Mg Zn Fe Pb H Cu Ag
Zn(s) + H2O(s) + H2O(g) -> ZnO(s) +H2(g) Zinc oxide is yellow when hot and white when cold 3Fe(s) + 4H2O(g) -> Fe3O4(g) Reacts slowly, iron must be heated constantly
No reaction
A more reactive metal can displace a less reactive metal from its salt solution (redox reaction) A more reactive metal can reduce the oxide of a less reactive metal
Metal carbonate Potassium carbonate Sodium carbonate Calcium carbonate Magnesium carbonate Zinc carbonate Iron (II) carbonate Lead(II) carbonate Copper(II) carbonate Silver carbonate
Action of heat on metal carbonates Observation Unaffected by heat Decompose into metal oxide and carbon dioxide on heating
Decomposes into silver and carbon dioxide on heating
Extracting iron from haematite 1 Carbon dioxide is produced
C(s) + O2(g) -> CO2(g)
2 Carbon monoxide is produced C(s) + CO2(g) -> 2CO(g)
3 Haematite is reduced to iron Fe2O3(s) + 3CO(g) -> 2Fe(l) + 3CO2(g)
4 Impurities are removed CaCO3(s) -> CaO(s) + CO2(g) CaO(s) + SiO2(s) -> CaSiO3(l)
Compiled by Ethan Wu Ying Tang
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