WAEC 2018 CHEMISTRY PRACTICAL ANSWERS Please use your school endpoint 1) Tabulate Burette reading|Final burette reading (cm^3)|Initial burette reading (cm^3)| Volume of acid used(cm^3)| Rough- 24.10,0.00,24.10 First- 23.80, 0.00, 23.80 Second- 23.75, 0.00, 23.70 Third- 23.75, 0.00, 23.75 Average volume of A used = 23.80 + 23.70 + 23.75cm^3/3 =23.75cm^3 1bi) Con in mol/dm3=conc in g/dm^3/molar mass con of B in g/dm^3 =4.80/0.25 =19.2g/ dm^3 molar mass = Fe+2Cl = 56+2(35.5)=127g/ mol conc in mol/dm^3 =19.2/127 =0.15mol/ dm^3 1bii) using CAVA/CBVB = NA/NB CA*11.80/0.15*20=1/5 CA=0.15*20*1/11.80*5 CA=0.05moldm^-3 1biii) mole =con(mol/dm^3)x vol (dm^3) =0.15*20/1000 =0.003moles. 2a) -Observation- part of the C dissolves,colourless filtrate salt -Inference- C is a mixture of soluble salt 2bi) -observation- white precipitate formed -Inference- Cl is present 2bii) -Observation- precipitate dissolves -Inference- Cl confirmed 2biii) -Observation- colourless gas evolved with characteristic choking smell, turns litimus paper blue -Inference- Gas is NH3 2c) -Observation- Residue dissolves liberating a colourless gas which turns lime water milky -Inference- gas is CO2 CO^2-3 present 3a)A white precipitate of barium sulphate will be formed by the instant reaction between barium chloride and sulphuric acid. BaCl2 + H2SO4 = BaSO4 + 2HCl 3b)Iron sulfide reacts with hydrochloric acid, releasing the malodorous (rotten egg smell) and very toxic gas,hydrogen sulphide. FeS + 2 HCl → FeCl2+ H2S 3c)When solid iron filings are added to dilute aqueous Hydrochloric acid, Iron (II)chloride or ferrous chloride is formed , with the liberation of Hydrogen gas. Fe (s) + 2HCl (aq) ……..> FeCl2(aq) + H2 (g) ========================= For WAEC 2018 CHEMISTRY PRACTICAL
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Created at 2018-04-07 13:46:32
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