Edexcel IGCSE Chemistry Chapter 10, page 88 ANSWERS 1 ... - AKIS

Edexcel IGCSE Chemistry Chapter 10, page 88 ANSWERS

1 Refer to Fig 10.4, p 82 The colour indicates the ion that determines solubility (or insolubility) soluble Sodium chloride Zinc nitrate Iron (III) sulfate Potassium sulfate Aluminium nitrate Ammonium chloride Magnesium nitrate Calcium sulfate (partly soluble) Sodium phosphate Potassium dichromate (IV)

insoluble Lead (II) sulfate Calcium carbonate Lead (II) chloride Copper (II) carbonate Silver chloride Barium sulfate Nickel (II) carbonate Chromium (III) hydroxide

2 a) The method is identical to that for making MgSO4, described on pages 83 – 84. b) (i) CuO(s) + H2SO4(aq) (ii) CuSO4(aq) + 5H2O(l)

CuSO4(aq) + H2O(l) CuSO45H2O(s)

3 a) phrase Using a pipette

Few drops methyl orange added Until solution became orange Without methyl orange Evaporated until sample crystallized on cooling in air Solution left to cool

b) (i) Na2CO3(s) + H2SO4 (aq) (ii) Na2SO4(aq)

+ 10H2O(l)

reason Precise measurement of the volume of sodium carbonate solution is important to find the precise amount of acid that must be added. We will be repeating the experiment without indicator to make sodium sulfate. The purity of sulfate made will depend on the precision of our measurements at this point. To show when the solution is neutral The solution is neutral when indicator just turns orange So that our solution contains only Na+, SO42- and H2O Speeds up the time until crystals begin to form Fully hydrated crystals will grow as the remaining water evaporated Na2SO4(aq)



+

Na2SO4 10H2O(s)

H2O(l)

+ CO2(g)

Edexcel IGCSE Chemistry Chapter 10, page 88 ANSWERS

4 Below are examples only. Other combinations of solutions are also possible (refer to Fig 10.4, p 82) a) silver nitrate + sodium chloride Ag+ (aq) + NO3-(aq) + Na+(aq) + Cl-(aq)

AgCl(s) + NO3-(aq) + Na+(aq)

b) sodium carbonate + calcium chloride 2Na+ (aq) + CO3-(aq) + Ca2+(aq) + 2Cl-(aq)

CaCO3(s) + 2Na+ (aq) + 2Cl-(aq)

c) lead (II) nitrate + copper sulfate Pb2+ (aq) + 2NO3-(aq) + Cu2+(aq) + SO42-(aq)

PbSO4(s) + 2NO3-(aq) + Cu2+(aq)

d) lead (II) nitrate + sodium chloride Pb2+ (aq) + 2NO3-(aq) + Na+(aq) + Cl-(aq)

PbCl2(s) + 2NO3-(aq)

+ Na+(aq)

5 Use a soluble barium salt and a soluble carbonate, e.g. barium nitrate and sodium carbonate. The ionic equation will be: Ba2+ (aq) + 2NO3-(aq) + 2Na+(aq) + CO32-(aq)

BaCO3(s) + 2NO3-(aq) + 2Na+(aq)

Mix the solutions and you will obtain a white precipitate of barium carbonate. Filter. Rinse the precipitate with distilled water to get rid of the nitrate and sodium ions. Leave the washed precipitate to dry on the filter paper. 6 a) zinc sulfate is soluble: use an acid with excess of solid i.e. zinc metal with dilute sulfuric acid. Evaporate at room temperature to obtain zinc sulfate crystals. Zn(s) + 2H+(aq) + SO42-(aq)

ZnSO4(aq)

+ H2(g)

b) barium sulfate is insoluble: use precipitation from solution of barium nitrate with dilute sulfuric acid. Ba2+ (aq) + 2NO3-(aq) + 2H+(aq) + SO42-(aq)

BaSO4(s) + 2NO3-(aq) + 2H+(aq)

c) potassium nitrate is soluble: use a titration of potassium hydroxide solution and dilute nitric acid. Establish the volumes to be used by using an indicator first, then perform the titration without the indicator. Evaporate at room temperature to obtain potassium nitrate crystals. K+ (aq) + OH-(aq) + H+(aq)+ NO3-(aq)

KNO3-(aq) + H2O(l)

Edexcel IGCSE Chemistry Chapter 10, page 88 ANSWERS

d) copper nitrate (II) is soluble: use an acid with excess of solid i.e. copper oxide and nitric acid. Use excess copper oxide, then filter and evaporate the filtrate. CuO(s) + HNO3(aq)

CuNO3(aq) + H2O(l)

e) lead (II) chromate is insoluble: use precipitation from solution of lead nitrate and solution of potassium chromate (IV) Pb2+ (aq) + 2NO3-(aq) + 2K+(aq) + CrO42-(aq)

BaCrO4(s) + 2NO3-(aq) + 2K+(aq)