Chemsitry Formulas For O Level Chemistry By Ethan Wu, Cheat Sheet of Chemistry

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Compiled by Ethan Wu Ying Tang All Chemistry Formulas for O levels Chemistry by Ethan Wu Hydrogen carbonate HCO3 - Hydride H- Hydroxide OH- Carbonate CO3 2- Nitrate NO3 - Nitrite NO2 - Nitride N3- Phosphate PO4 3- Sulfate SO4 2- Sulfite SO3 2- Sulfide S2- Ammonia NH3 Ammonium ion NH4 + Mole Concept One mole of any substance contains 6 X 1023 particles (Avogadro’s number). 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 = 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒𝑠 6 × 1023 The molar mass of an element is the mass of one mole of atoms of the element. 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑎𝑛 𝑒𝑙𝑒𝑚𝑒𝑛𝑡 = 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑡ℎ𝑒 𝑒𝑙𝑒𝑚𝑒𝑛𝑡 𝑖𝑛 𝑔 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑡ℎ𝑒 𝑒𝑙𝑒𝑚𝑒𝑛𝑡 𝑖𝑛 𝑔/𝑚𝑜𝑙 Percentage composition of compounds 𝑝𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑏𝑦 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑎𝑛 𝑒𝑙𝑒𝑚𝑒𝑛𝑡 𝑖𝑛 𝑎 𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑 = 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑎𝑡𝑜𝑚𝑠 𝑜𝑓 𝑒𝑙𝑒𝑚𝑒𝑛𝑡 × 𝐴𝑟 𝑀𝑟 𝑜𝑓 𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑 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 𝑛 = 𝑟𝑒𝑙𝑎𝑡𝑖𝑣𝑒 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑡ℎ𝑎𝑛𝑒 𝑟𝑒𝑙𝑎𝑡𝑖𝑣𝑒 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑡ℎ𝑎𝑛𝑒 𝑓𝑟𝑜𝑚 𝑒𝑚𝑝𝑖𝑟𝑖𝑐𝑎𝑙 𝑓𝑜𝑟𝑚𝑢𝑙𝑎 Compiled by Ethan Wu Ying Tang Molar volume of gases 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑔𝑎𝑠 = 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑔𝑎𝑠 𝑖𝑛 𝑐𝑚3𝑎𝑡 𝑟. 𝑡. 𝑝. 24 000 𝑐𝑚3 Concentration of a solution (can be in terms of mol/dm3 or g/dm3) 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑖𝑛 𝑔/𝑑𝑚3 = 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝑖𝑛 𝑔 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑖𝑛 𝑑𝑚3 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝑖𝑛 𝑚𝑜𝑙/𝑑𝑚3 = 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑖𝑛 𝑑𝑚3 𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑦𝑖𝑒𝑙𝑑 = 𝑎𝑐𝑡𝑢𝑎𝑙 𝑦𝑖𝑒𝑙𝑑 𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑦𝑖𝑒𝑙𝑑 × 100% 𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑝𝑢𝑟𝑖𝑡𝑦 = 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑝𝑢𝑟𝑒 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒 𝑖𝑛 𝑠𝑎𝑚𝑝𝑙𝑒 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒 × 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 Zinc No reaction Zn(s) + H2O(s) + H2O(g) -> ZnO(s) +H2(g) Zinc oxide is yellow when hot and white when cold Iron No reaction (except rusting) 3Fe(s) + 4H2O(g) -> Fe3O4(g) Reacts slowly, iron must be heated constantly Lead Copper Silver No reaction No reaction Most reactive to least reactive K Na Ca Mg Zn Fe Pb H Cu Ag 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 Action of heat on metal carbonates Metal carbonate Observation Potassium carbonate Sodium carbonate Unaffected by heat Calcium carbonate Magnesium carbonate Zinc carbonate Iron (II) carbonate Lead(II) carbonate Copper(II) carbonate Decompose into metal oxide and carbon dioxide on heating Silver carbonate 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 Hardest to discharge to easiest to discharge K+ Na+ Ca2+ MG2+ Zn2+ Fe2+ Pb2+ H+ Cu2+ Ag+ Hardest to discharge to easiest to discharge SO4 2- NO3 - Cl- Br- I- OH- Manufacturing ammonia by Haber process Nitrogen + hydrogen ⇌ ammonia (added in the ratio 1:3) N2(g) + 3H2(g) -⇌ 2NH3(g) Conditions: 250atm, 450°C, iron as catalyst Only about 10-15% of nitrogen and hydrogen concerted to ammonia (ammonia gas cooled to liquid) SO2 + H2O -> H2SO3 sulfurous acid Sulfurous acid can be oxidized in air to form sulfuric acid 4NO2 + 2H2O + O2 -> 4HNO3 Reducing pollution Catalytic converters 2CO(g) + O2(g) -> 2CO2(g) 2NO(g) + 2CO(g) -> N2(g) + 2CO2(g) 2C8H18(l) + 25O2(g) -> 16CO2(g) + 18H2O(g) Flue Gas Desulfurisation (remove sulfur dioxide pollution) CaCO3(s) + SO2(g) -> CaSO3(S) + CO2 2CaSO3(s) + O2(g) -> 2CaSO4(s) CaO(s) + SO2(g) -> CaSO3(s) Alkanes Combustion Alkane + oxygen -> carbon dioxide + water vapour Substitution (under ultraviolet light) E.g. methane + chlorine -> chloromethane + hydrogen chloride Alkenes Combustion Alkene + oxygen -> carbon dioxide + water vapour As alkenes have higher percentage of carbon than alkanes, alkenes will burn with a sootier flame Alkenes can also undergo substitution reaction under UV light An Addition reaction is a reaction in which an unsaturated organic compound combines with another substance to form a single new compound  Addition of hydrogen Ethene + hydrogen -> ethane Conditions: 200°C, nickel as catalyst Convert vegetable oils to solid margarine  Addition of bromine Compiled by Ethan Wu Ying Tang Ethene + bromine -> 1,2-dibromooethane Serve as a chemical test to distinguish between alkane and alkene  Addition of steam Ethene + steam -> ethanol Conditions: 300°C, 60 atm, phosphoric (V) acid as catalyst  Addition polymerization Ethene -> poly(ethene) Conditions: High temperature and pressure and catalyst Alcohol  Combustion Alcohol + oxygen -> carbon dioxide + water vapour Can be used as a fuel Burnt on some food such as fruit cake to give it a distinct flavor  Oxidation Alcohol + oxidizing agent -> carboxylic acid + water C2H5OH + 2[O] -> CH3COOH +H2O (2 ways oxidation by acidified potassium manganate (VII) and oxidation by atmospheric oxygen) Breathalyzer contains an oxidizing agent that has a colour agent when high level of alcohol detected Producing ethanol  From catalytic addition of steam to ethene  Alcohol fermentation Glucose -> ethanol + carbon dioxide Carboxylic acids Are weak acids Reaction with reactive metals (salts of ethanoic acid are known as ethanoates) Reaction with carbonates Reaction with bases Reaction with alcohols to produce ester and water (esterification) Ester An ester is a colourless liquid that is insoluble in water Ethanoic acid + methanol -> methyl ethanoate (concentrated sulfuric acid as catalyst) First part of name from alcohol Functional group Polymerization Additional polymerization occurs when unsaturated monomers join together without losing any molecules or atoms. Condensation polymerization occurs when monomers combine to form a polymer with the removal of a small molecule such as water.