Acid, Bases and Salts (IGCSE Chemistry Syllabus )

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1 Acid, Bases and Salts (IGCSE Chemistry Syllabus ) Acid o A compound when dissolved in water produces hydrogen ions (H + ) ; proton (H + ) donor o It turns blue damp litmus paper to red o ph 1 to 6 o Strong acid: ionizes completely and produces high concentration of H+ ions o Weak acid: ionizes partially and produces low concentration of H+ ions o Reactions: neutralization i. Acid + Metal Salt + Hydrogen 2HCl + 2Na 2NaCl + H2 ii. Acid + Metal Oxide Salt + Water 2HCl + Na2O 2NaCl + H2O iii. Acid + Metal Carbonate Salt + Carbon Dioxide + Water 2HCl + Na2CO3 2NaCl + CO2 + H2O iv. Acid + Metal Hydroxide Salt + Water HCl + NaOH NaCl + H2O Bases o Can be categorized into soluble (alkali) and insoluble bases o Proton acceptors o Turns red damp litmus paper into blue o ph 8 to 14 o e.g. of bases: Metal, Metal Carbonate, Metal Hydroxide, Metal Oxide o Strong alkali: completely ionize in water and produces high concentration of OH- ions o Weak alkali: partially ionize in water and produces low concentration of OH- ions o Reactions: neutralization i. Acid + Metal Salt + Hydrogen 2HCl + 2Na 2NaCl + H2 ii. Acid + Metal Oxide Salt + Water 2HCl + Na2O 2NaCl + H2O iii. Acid + Metal Carbonate Salt + Carbon Dioxide + Water 2HCl + Na2CO3 2NaCl + CO2 + H2O iv. Acid + Metal Hydroxide Salt + Water HCl + NaOH NaCl + H2O v. Base + Ammonium Salt Salt + Ammonia + Water NaOH + NH4Cl NaCl + NH3 + H2O 1

2 ph o Litmus paper o Universal Indicator o Methyl Orange o Phenolphthalein Controlling Acidity in Soil o Plants grow at a ph near 7 o If it is too acidic or alkaline they will not grow o Acidic soil is fixed by adding lime 2

3 Types of Oxides Basic Oxide - Group 1 & 2 and transition e.g. Na2O, MgO, Fe2O3 metal oxide - React with acid Acidic Oxide - Non-metal oxide e.g. CO2, NO2, SO2 - React with base Amphoteric Oxide - Aluminium, zinc and lead e.g. Al2O3, ZnO and PbO Neutral Oxide - Monoxide e.g. CO, H2O Salts Salt Soluble salt Insoluble salt Acid + Metal Double decomposition of two soluble salt / Precipitation Acid + Metal Oxide Acid + Metal Carbonate Acid + Metal Hydroxide 3

4 Soluble Salt Preparation E.g. To prepare NaCl i. Acid + Metal Salt + Hydrogen 2HCl + 2Na 2NaCl + H2 ii. Acid + Metal Oxide Salt + Water 2HCl + Na2O 2NaCl + H2O iii. Acid + Metal Carbonate Salt + Carbon Dioxide + Water 2HCl + Na2CO3 2NaCl + CO2 + H2O 4

5 iv. Acid + Metal Hydroxide Salt + Water HCl + NaOH NaCl + H2O Insoluble Salt Preparation E.g. To prepare AgCl 2AgNO3(aq) + PbCl2(aq) 2AgCl(s) + Pb(NO3)2 (aq) 5

6 Soluble and Insoluble Salt Formula of Soluble and Insoluble Salt ** Insoluble Salt: Carbonate, Hydroxide 6

Test for Cations Sodium Hydroxide - Few drops of NaOH added to aqueous cation - All cations will form precipitate - Non-transition metal cations: white precipitate - Transition metal cations: Iron

7 Test for Cations Sodium Hydroxide - Few drops of NaOH added to aqueous cation - All cations will form precipitate - Non-transition metal cations: white precipitate - Transition metal cations: Iron (II): green precipitate Iron (III): brown precipitate Copper: blue precipitate - Excess of NaOH added to aqueous cation Ammonia - Few drops of NH3 added to aqueous cation - All cations will form precipitate - Non-transition metal cations: white precipitate - Transition metal cations: Iron (II): green precipitate Iron (III): brown precipitate Copper: blue precipitate - Excess of NH3 added to aqueous cation - Zn, Al and Pb dissolve in excess of NaOH to form colourless solution - Zn and Ca dissolve in excess of NH3 to form colourless solution - Cu dissolve in excess of NH3 to form royal blue solution Test for Anions Chloride Bromide Iodide - Add dilute nitric acid and silver nitrate AgCl: white precipitate AgBr: cream precipitate AgI: yellow precipitate BaSO4: white precipitate Sulphate - Add dilute nitric acid and barium nitrate Carbonate - Add acid Carbon dioxide gas releases Limewater turns milky Nitrate - Add sodium hydroxide then add aluminium Ammonia gas releases Gas produced turns damp red litmus paper blue 7

8 Test for Gases Ammonia Carbon Dioxide Chlorine Hydrogen Oxygen Damp red litmus paper turns blue Turns limewater milky Bleaches red/blue litmus paper Lighted splinter, pop sound RELIGHT Glowing splinter 8

Identification of Ions and Gases

Identification of Ions and Gases Question Paper 1 Level IGSE Subject hemistry (0620/0971) Exam oard ambridge International Examinations (IE) Topic cids, bases and salts Sub-Topic Identification of ions