RI Y4 Chem 2022 FE Revision Acids Bases Salts Ionic Eqn ANS

1 Raffles Institution Raffles Programme Year Four Chemistry Name: ____________________________ ( ) Class: ______ Date: _______ 2022 FE Revision – Acids, Bases and Salts; Ionic Equations Answers nitric acid HNO3 calcium hydroxide Ca(OH)2 sulfuric acid H2SO4 ammonia NH3 ethanoic acid CH3COOH copper(II) oxide CuO Reactions of Acids 1 HCl + NaOH  NaCl + H2O 2 2HNO3 + CaCO3  Ca(NO3)2 + H2O + CO2 3 H2SO4 + Mg  MgSO4 + H2 Reactions of Bases 1 CaO + 2HCl  CaCl2 + H2O 2 NaOH + NH4Cl  NaCl + H2O + NH3 3 2NaOH + Fe(NO3)2  2NaNO3 + Fe(OH)2 green ppt 2NaOH + CuSO4  Na2SO4 + Cu(OH)2 blue ppt Strength of Acids and Bases 1 A strong acid is one that completely ionises/dissociates in water while a weak acid is one that partially ionises/dissociates in water 2(a) (i) strong acid (ii) strong base (iii) + H+(aq) weak acid (iv) + OH−(aq) weak base 2(b) CH3COOH + KOH  CH3COOK + H2O 2CH3COOH + Na2CO3  2NaCH3COO + H2O + CO2 2CH3COOH + Mg  (CH3COO)2Mg + H2 ⇌ 2H+ + 3 A 10 mol dm–3 solution of hydrochloric acid is a concentrated solution of a strong acid while a 0.1 mol dm–3 solution of hydrochloric acid is a dilute solution of a strong acid. 4 (strong) acid, concentration [H+] / mol dm−3 pH sulfuric acid, H2SO4, 0.0100 mol dm−3 H2SO4 is dibasic: 1 mol H2SO4 dissociates to produce 2 mol H+ 0.0200 −lg (0.0200) = 1.70 Solubility rules and Precipitation reactions sulfate most, except… BaSO4, calcium sulfate and PbSO4 chloride most, except… silver chloride and PbCl2 iodide most, except… AgI and Lead(II) iodide O C CH2 C O O O-- Acid-Base titrations Titration pH of equivalence point circle your choice strong alkali - strong acid <7 / =7 / >7 strong alkali - weak acid <7 / =7 / >7 * weak alkali - strong acid <7 / =7 / >7 * Types of Oxides Na2O + 2HCl → 2NaCl + H2O CuO + H2SO4 → CuSO4 + H2O ZnO CO2 + 2NaOH → Na2CO3 + H2O SiO2 + CaO → CaSiO3

2 aqueous silver nitrate and aqueous sodium iodide / potassium iodide silver iodide aqueous zinc nitrate and aqueous sodium carbonate zinc carbonate aqueous iron(III) nitrate and aqueous sodium hydroxide iron(III) hydroxide aqueous lead(II) nitrate and aqueous sodium chloride lead(II) chloride 1 Na2CO3 (aq) + CaCl2 (aq)  2NaCl (aq) + CaCO3 (s) 2 2NaOH (aq) + CuSO4 (aq)  Cu(OH)2 (s) + Na2SO4 (aq) Writing Ionic Equations Cl2 (g) + 2I– (aq)  2Cl– (aq) + I2 (s) Cu2+ (aq) + Zn (s)  Zn2+ (aq) + Cu (s) (a) 3OH− (aq) + Fe3+ (aq)  Fe(OH)3 (s) red-brown precipitate: iron(III) hydroxide (b) Ag+ (aq) + Cl− (aq)  AgCl (s) white precipitate: silver chloride Practice Questions 1 D 2 D 3 A 4 D 5 C 6 method compound (a) precipitation magnesium carbonate reactants: aqueous magnesium nitrate and aqueous sodium carbonate equation: Mg(NO3)2 (aq) + Na2CO3 (aq)  MgCO3 (s) + 2NaNO3 (aq) (b) titration sodium nitrate reactants: aqueous sodium hydroxide and dilute nitric acid equation: NaOH (aq) + HNO3 (aq)  NaNO3 (aq) + H2O (l) (c) reaction between excess metal oxide and dilute acid copper(II) chloride reactants: copper(II) oxide and dilute hydrochloric acid equation: CuO (s) + 2HCl (aq)  CuCl2 (aq) + H2O (l) (d) reaction between excess metal and dilute acid zinc sulfate reactants: zinc and dilute sulfuric acid equation: Zn (s) + H2SO4 (aq)  ZnSO4 (aq) + H2 (g) 7(a) Lead(II) chloride is an insoluble compound. When dilute hydrochloric acid reacts with lead(II) oxide, which is also not soluble in water, a solid coating of lead(II) chloride forms around lead(II) oxide, preventing lead(II) oxide from further reacting with hydrochloric acid, which means the reaction will stop. 7(b) reactants: aqueous lead(II) nitrate and aqueous sodium chloride (or dilute hydrochloric acid) procedure: step 1: mix aqueous lead(II) nitrate and aqueous sodium chloride in a beaker step 2: filter the mixture, collect the residue, which is lead(II) chloride step 3: wash the residue with distilled water and air-dry the solid or dry between sheets of filter paper 8(a) 8(b) Hydrochloric acid is a strong acid while ethanoic acid is a weak acid. The two acids have the same concentration. Since hydrochloric acid is fully dissociated, it will have a higher concentration of aqueous hydrogen ions and hence, a lower pH (of 1). Ethanoic acid dissociates partially and will produce a lower concentration of aqueous hydrogen ions. The pH will be higher (at 3).