JK-TK/Newdata huggingface dataset:
At this temperature ,the Oxygen evolved/produced at the anode reacts with carbon anode to form carbon(IV)oxide gas that escape to the atmosphere. C(s) + O2(g) CO2(g) The anode thus should be continuously replaced from time to time. Flow chart summary of extraction of aluminium from Bauxite Bauxite(Al2O3.2H2O) ore with impurities Fe2O3 and SiO2 Powdered mixture Crush (increase surface area) Hot concentrated sodium hydroxide
14 c) Diagram showing the Hall cell / process for extraction of Bauxite Iron(III)oxide- Fe2O3 as residue Sodium aluminate (NaAl(OH)4) and sodium silicate (Na2SiO3) as filtrate Carbon(IV)oxide Aluminium hydroxide (Al(OH)3) as residue Sodium silicate (Na2SiO3) Aluminium (III) Oxide Roast at 1000oC Cryolite Electrolysis Oxygen gas at anode Pure aluminium sinks in Hall cell
15 d)Uses of aluminium (i) In making aeroplane parts, buses, tankers, furniture because aluminium is very light. (ii)Making duralumin-an alloy which is harder and has a higher tensile strength (iii)Making utensils,sauce pans,spoons because it is light and good conductor of electricity. (iv)Making overhead electric cables because it is light,ductile and good conductor of electricity. (iv)Used in the thermite process for production of Manganese, Chromium amd Titanium. e) Environmental effects of extracting aluminium from Bauxite. Carbon(IV)oxide gas that escape to the atmosphere is a green house gas that causes global warming. Bauxite is extracted by open caste mining that causes soil/environmental degradation. 16 f) Test for presence of Al3+ If an ore is suspected to contain Al3+ it is; (i)added hot concentrated sulphuric(VI)/Nitric(V)acid to free the ions present. (ii)the free ions are then added a precipitating reagent like 2M sodium hydroxide /2M aqueous ammonia.
Bauxite is extracted by open caste mining that causes soil/environmental degradation. 16 f) Test for presence of Al3+ If an ore is suspected to contain Al3+ it is; (i)added hot concentrated sulphuric(VI)/Nitric(V)acid to free the ions present. (ii)the free ions are then added a precipitating reagent like 2M sodium hydroxide /2M aqueous ammonia. Observation Inference White precipitate in excess 2M NaOH(aq) Pb2+ , Al3+, Zn2+ White precipitate in excess 2M NH3(aq) Pb2+ , Al3+ No black precipitate on adding Na2S(aq) Al3+ No white precipitate on adding either NaCl(aq),HCl(aq),H2SO4(aq),Na2SO4(aq) Al3+ Practice 1.An unknown rock X was discovered in Ukraine. Test with dilute sulphuric (VI)acid shows rapid effervescence with production of a colourless gas A that forms a white precipitate with lime water and colourless solution B. On adding 3cm3 of 2M sodium hydroxide, a white precipitate C is formed that dissolves to form a colourless solution D on adding more sodium hydroxide. On adding 2M aqueous ammonia, a white precipitate E is formed which persist in excess aqueous ammonia.On which on adding 5cm3 of 1M Lead(II)nitrate(V) to F a white precipitate G is formed which remains on heating. Identify: A Hydrogen/H2 B Aluminium sulphate(VI)/Al2(SO4) 3 C Aluminium hydroxide/ Al(OH4) 3 D Tetrahydroxoaluminate(III)/ [Al(OH4) 3] - E Aluminium hydroxide/ Al(OH) 3 F Aluminium chloride/ AlCl3
17 2.Aluminium is obtained from the ore with the formula Al2O3. 2H2O. The ore is first heated and refined to obtain pure aluminium oxide (Al2O3). The oxide is then electrolysed to get Aluminium and oxygen gas using carbon anodes and carbon as cathode.
2H2O. The ore is first heated and refined to obtain pure aluminium oxide (Al2O3). The oxide is then electrolysed to get Aluminium and oxygen gas using carbon anodes and carbon as cathode. Give the common name of the ore from where aluminium is extracted from ½ mark What would be the importance of heating the ore first before refining it?1 mark To remove the water of crystallization The refined ore has to be dissolved in cryolite first before electrolysis. Why is this necessary? 1½ mark To lower the melting point of aluminium oxide from about 2015oC to 900oC so as to lower /reduce cost of production Why are the carbon anodes replaced every now and then in the cell for electrolysing aluminium oxide? 1 mark Oxygen produced at anode react with carbon to form carbon(IV)oxide gas that escape State two uses of aluminium In making aeroplane parts, buses, tankers, utensils, sauce pans,spoons Making overhead electric cables Making duralumin
18 3. IRON a)Natural occurrence Iron is the second most common naturally occurring metal. It makes 4% of the earths crust as: (i)Haematite(Fe2O3) (ii)Magnetite(Fe3O4) (iii)Siderite(FeCO3) b)The blast furnace for extraction of iron from Haematite and Magnetite a)Raw materials: (i)Haematite(Fe2O3) (ii)Magnetite(Fe3O4) (iii)Siderite(FeCO3) (iv)Coke/charcoal/ carbon (v)Limestone b)Chemical processes: Iron is usually extracted from Haematite (Fe2O3), Magnetite(Fe3O4) Siderite (FeCO3).These ores contain silicon(IV)oxide(SiO2) and aluminium(III)oxide (Al2O3) as impurities. When extracted from siderite, the ore must first be roasted in air to decompose the iron(II)Carbonate to Iron(II)oxide with production of carbon(IV)oxide gas: FeCO3(s) FeO(s) + CO2(g) Iron(II)oxide is then rapidly oxidized by air to iron(III)oxide(Haematite).
IRON a)Natural occurrence Iron is the second most common naturally occurring metal. It makes 4% of the earths crust as: (i)Haematite(Fe2O3) (ii)Magnetite(Fe3O4) (iii)Siderite(FeCO3) b)The blast furnace for extraction of iron from Haematite and Magnetite a)Raw materials: (i)Haematite(Fe2O3) (ii)Magnetite(Fe3O4) (iii)Siderite(FeCO3) (iv)Coke/charcoal/ carbon (v)Limestone b)Chemical processes: Iron is usually extracted from Haematite (Fe2O3), Magnetite(Fe3O4) Siderite (FeCO3).These ores contain silicon(IV)oxide(SiO2) and aluminium(III)oxide (Al2O3) as impurities. When extracted from siderite, the ore must first be roasted in air to decompose the iron(II)Carbonate to Iron(II)oxide with production of carbon(IV)oxide gas: FeCO3(s) FeO(s) + CO2(g) Iron(II)oxide is then rapidly oxidized by air to iron(III)oxide(Haematite). 4FeO(s) + O2(g) 2Fe2O3(s) Haematite (Fe2O3), Magnetite(Fe3O4), coke and limestone are all then fed from top into a tall (about 30metres in height) tapered steel chamber lined with refractory bricks called a blast furnace. The furnace is covered with inverted double cap to prevent/reduce amount of any gases escaping . Near the base/bottom, blast of hot air at about 1000K (827oC) is driven/forced into the furnace through small holes called Tuyeres. As the air enters ,it reacts with coke/charcoal/carbon to form carbon(IV)oxide gas. This reaction is highly exothermic. C(s)+ O2(g) CO2 (g) ∆H = -394kJ
19 This raises the temperature at the bottom of the furnace to about 2000K(1650oC).As Carbon(IV)oxide gas rises up the furnace it reacts with more coke to form carbon(II)oxide gas.This reaction is endothermic.
As the air enters ,it reacts with coke/charcoal/carbon to form carbon(IV)oxide gas. This reaction is highly exothermic. C(s)+ O2(g) CO2 (g) ∆H = -394kJ
19 This raises the temperature at the bottom of the furnace to about 2000K(1650oC).As Carbon(IV)oxide gas rises up the furnace it reacts with more coke to form carbon(II)oxide gas.This reaction is endothermic. CO2 (g) + C(s) 2CO (g) ∆H = +173kJ Carbon(II)oxide gas is a strong reducing agent that reduces the ores at the upper parts of the furnace where temperatures are about 750K(500oC) i.e. For Haematite; Fe2O3 (s) + 3CO(g) 2Fe(s) + CO2(g) For Magnetite; Fe3O4 (s) + 4CO(g) 3Fe(s) + 4CO2(g) Iron is denser than iron ore. As it falls to the hotter base of the furnace it melts and can easily be tapped off. Limestone fed into the furnace decomposes to quicklime/calcium oxide and produce more carbon(IV)oxide gas. CaCO3(s) CaO(s) + CO2(g) Quicklime/calcium oxide reacts with the impurities silicon(IV)oxide(SiO2) and aluminium(III)oxide(Al2O3)in the ore to form calcium silicate and calcium aluminate. CaO(s) + SiO2(s) CaSiO3 (l) CaO(s) + Al2O3(s) Ca Al2O4 (l) Calcium silicate and calcium aluminate mixture is called slag.Slag is denser than iron ore but less dense than iron therefore float on the pure iron. It is tapped at different levels to be tapped off for use in: (i)tarmacing roads (ii) cement manufacture (iii)as building construction material (c)Uses of Iron Iron obtained from the blast furnace is hard and brittle. It is called Pig iron. It is remelted, added scrap steel then cooled. This iron is called cast iron. Iron is mainly used to make: (i)gates ,pipes, engine blocks, rails, charcoal iron boxes,lamp posts because it is cheap.
It is remelted, added scrap steel then cooled. This iron is called cast iron. Iron is mainly used to make: (i)gates ,pipes, engine blocks, rails, charcoal iron boxes,lamp posts because it is cheap. 20 (ii)nails, cutlery, scissors, sinks, vats, spanners,steel rods, and railway points from steel. Steel is an alloy of iron with carbon, and/or Vanadium, Manganese, Tungsten, Nickel ,Chromium. It does not rust/corrode like iron. e) Environmental effects of extracting Iron from Blast furnace (i)Carbon(IV)oxide(CO2) gas is a green house gas that causes/increases global warming if allowed to escape/leak from the furnace. (ii)Carbon(II)oxide(CO)gas is a highly poisonous/toxic odourless gas that can kill on leakage. It is preferentially absorbed by the haemoglobin in mammals instead of Oxygen to form a stable compound that reduce free hemoglobin in the blood. (iii) Haematite (Fe2O3), Magnetite(Fe3O4) and Siderite (FeCO3) are extracted through quarrying /open cast mining that cause soil / environmental degradation . 21 f) Test for the presence of Iron Iron naturally exist in its compound as Fe2+ /Fe3+ If an ore is suspected to contain Fe2+ /Fe3+ it is; (i)added hot concentrated sulphuric(VI)/Nitric(V)acid to free the ions present. (ii)the free ions are then added a precipitating reagent like 2M sodium hydroxide /2M aqueous ammonia which forms; I) an insoluble green precipitate in excess of 2M sodium hydroxide /2M aqueous ammonia if Fe2+ ions are present. I) an insoluble brown precipitate in excess of 2M sodium hydroxide /2M aqueous ammonia if Fe2+ ions are present.
21 f) Test for the presence of Iron Iron naturally exist in its compound as Fe2+ /Fe3+ If an ore is suspected to contain Fe2+ /Fe3+ it is; (i)added hot concentrated sulphuric(VI)/Nitric(V)acid to free the ions present. (ii)the free ions are then added a precipitating reagent like 2M sodium hydroxide /2M aqueous ammonia which forms; I) an insoluble green precipitate in excess of 2M sodium hydroxide /2M aqueous ammonia if Fe2+ ions are present. I) an insoluble brown precipitate in excess of 2M sodium hydroxide /2M aqueous ammonia if Fe2+ ions are present. Observation Inference green precipitate in excess 2M NaOH(aq) Fe2+ green precipitate in excess 2M NH3(aq) Fe2+ brown precipitate in excess 2M NaOH(aq) Fe3+ brown precipitate in excess 2M NH3(aq) Fe3+ Practice questions
22 4.COPPER a)Natural occurrence Copper is found as uncombined element/metal on the earths crust in Zambia, Tanzania, USA and Canada .The chief ores of copper are: (i)Copper pyrites(CuFeS2) (ii)Malachite(CuCO3.Cu(OH)2) (iii)Cuprite(Cu2O) b)Extraction of copper from copper pyrites. Copper pyrites are first crushed into fine powder. The powdered ore is the added water and oil. The purpose of water is to dissolve hydrophilic substances/particle. The purpose of oil is to make cover copper ore particle so as to make it hydrophobic Air is blown through the mixture. Air creates bubbles that stick around hydrophobic copper ore. The air bubbles raise through buoyancy small hydrophobic copper ore particles to the surface. A concentrated ore floats at the top as froth. This is called froth flotation. The concentrated ore is then skimmed off.The ore is then roasted in air to form copper(I)sulphide ,sulphur(IV)oxide and iron (II) oxide.
A concentrated ore floats at the top as froth. This is called froth flotation. The concentrated ore is then skimmed off.The ore is then roasted in air to form copper(I)sulphide ,sulphur(IV)oxide and iron (II) oxide. 2CuFeS2(s) + 4O2(g) Cu2S(s) + 3SO2(g) + 2FeO(s) Limestone (CaCO3) and silicon(IV)oxide (SiO2) are added and the mixture heated in absence of air.Silicon(IV)oxide (SiO2) reacts with iron (II) oxide to form Iron silicate which constitutes the slag and is removed. FeO(s) + SiO2(s) FeSiO3(s) The slag separates off from the copper(I)sulphide. Copper(I)sulphide is then heated in a regulated supply of air where some of it is converted to copper (I) oxide. 2Cu2S (s) + 3O2(g) 2Cu2S(s) + 2SO2(g) The mixture then undergo self reduction in which copper(I)oxide is reduced by copper(I)sulphide to copper metal. Cu2S (s) + 2Cu2O (s) 6Cu (s) + SO2(g) The copper obtained has Iron, sulphur and traces of silver and gold as impurities.It is therefore about 97.5% pure. It is refined by electrolysis/electrolytic method. During the electrolysis of refining copper, the impure copper is made the anode and a small pure strip is made the cathode. Electrode ionization takes place where: At the anode;
23 Cu(s) Cu2+ (aq) + 2e Note: Impure copper anode dissolves/erodes into solution and decreases in size. At the Cathode; Cu2+ (aq) + 2e Cu(s) Note: The copper ions in the electrolyte(CuSO4) are reduced and deposited as copper metal at the cathode. The copper obtained is 99.98% pure. Valuable traces of silver and gold collect at the bottom of the electrolytic cell as sludge. It is used to finance the extraction of copper pyrites.
The copper obtained is 99.98% pure. Valuable traces of silver and gold collect at the bottom of the electrolytic cell as sludge. It is used to finance the extraction of copper pyrites. (c)Flow chart summary of extraction of copper from Copper pyrites Copper pyrites(CuFeS2) ore with impurities Fe2O3 and SiO2 Froth Crush (increase surface area) Oil Concentration chamber 1st roasting chamber Silicon(IV) oxide Smelting furnace 2nd roasting furnace Calcium aluminate (CaAl2O4)slag Limestone Sulphur(IV)Oxide Iron Silicate (FeSiO3)Slag Water Excess air Limited air Sulphur(IV)Oxide Self reduction Impure copper Rocky impurities Cu2S Cu2S, Cu2O Electrolysis using Copper electrodes
24 Electrolytic purification of impure copper d) Uses of copper Copper is mainly used in: (i)making low voltage electric cables,contact switches, cockets and plugs because it is a good conductor of electricity. (ii)Making solder because it is a good thermal conductor. (iii)Making useful alloys e.g. -Brass is an alloy of copper and Zinc(Cu/Zn) -Bronze is an alloy of copper and Tin(Cu/Sn) -German silver is an alloy of copper ,Zinc and Nickel(Cu/Zn/Ni) (iv)Making coins and ornaments. e) Environmental effects of extracting copper from Copper pyrites (i)Sulphur(IV)oxide is a gas that has a pungent poisonous smell that causes head ache to human in high concentration. (ii)Sulphur(IV)oxide gas if allowed to escape dissolves in water /rivers/rain to form weak sulphuric(IV)acid lowering the pH of the water leading to marine pollution, accelerated corrosion/rusting of metals/roofs and breathing problems to human beings. Anode; Impure Copper eroded. Cathode; Pure Copper deposited. 25 (iii)Copper is extracted by open caste mining leading to land /environmental /soil degradation.
Anode; Impure Copper eroded. Cathode; Pure Copper deposited. 25 (iii)Copper is extracted by open caste mining leading to land /environmental /soil degradation. f) Test for the presence of copper in an ore Copper naturally exist in its compound as Cu2+ /Cu+ Copper (I) / Cu+ is readily oxidized to copper(II)/ Cu2+ If an ore is suspected to contain Cu2+ /Cu+ it is; (i)added hot concentrated sulphuric(VI)/Nitric(V)acid to free the ions present. (ii)the free ions are then added a precipitating reagent; 2M sodium hydroxide /2M aqueous ammonia which forms; I) an insoluble blue precipitate in excess of 2M sodium hydroxide if Cu2+ ions are present. I) an insoluble blue precipitate in 2M aqueous ammonia that dissolve to royal/deep blue solution in excess if Cu2+ ions are present. Observation Inference blue precipitate in excess 2M NaOH(aq) Cu2+ blue precipitate,dissolve to royal/deep blue solution in excess 2M NH3(aq) Cu2+ g)Sample questions Copper is extracted from copper pyrites as in the flow chart outlined below. Study it and answer the questions that follow
26 5.ZINC and LEAD a)Natural occurrence Zinc occurs mainly as: (i)Calamine-Zinc carbonate(ZnCO3) (ii)Zinc blende-Zinc sulphide(ZnS) Lead occurs mainly as Galena-Lead(II)Sulphide mixed with Zinc blende: b)Extraction of Zinc/Lead from Calamine ,Zinc blende and Galena. During extraction of Zinc , the ore is first roasted in air: For Calamine Zinc carbonate decompose to Zinc oxide and carbon(IV) oxide gas. ZnCO3(s) ZnO(s) + CO2(g) Zinc blende does not decompose but reacts with air to form Zinc oxide and sulphur(IV) oxide gas. Galena as a useful impurity also reacts with air to form Lead(II) oxide and sulphur(IV) oxide gas.
During extraction of Zinc , the ore is first roasted in air: For Calamine Zinc carbonate decompose to Zinc oxide and carbon(IV) oxide gas. ZnCO3(s) ZnO(s) + CO2(g) Zinc blende does not decompose but reacts with air to form Zinc oxide and sulphur(IV) oxide gas. Galena as a useful impurity also reacts with air to form Lead(II) oxide and sulphur(IV) oxide gas. 2ZnS(s) + 3O2(g) 2ZnO(s) + 2SO2(g) (Zinc blende) 2PbS(s) + 3O2(g) 2PbO(s) + 2SO2(g) (Galena) The oxides are mixed with coke and limestone/Iron(II)oxide/ Aluminium (III) oxide and heated in a blast furnace. At the furnace temperatures limestone decomposes to quicklime/CaO and produce Carbon(IV)oxide gas. CaCO3(s) CaO(s) + CO2 (g) Carbon(IV)oxide gas reacts with more coke to form the Carbon(II)oxide gas. C(s) + CO2 (g) 2CO (g) Both Carbon(II)oxide and carbon/coke/carbon are reducing agents. 27 The oxides are reduced to the metals by either coke or carbon (II)oxide. ZnO(s) + C(s) Zn(g) + CO (g) PbO(s) + C(s) Pb(l) + CO (g) PbO(s) + CO(s) Pb(l) + CO2 (g) PbO(s) + CO(s) Pb(g) + CO2 (g) At the furnace temperature: (i)Zinc is a gas/vapour and is collected at the top of the furnace. It is condensed in a spray of molten lead to prevent reoxidation to Zinc oxide. On further cooling , Zinc collects on the surface from where it can be tapped off (ii)Lead is a liquid and is ale to trickle to the bottom of the furnace from where it is tapped off. Quicklime/CaO, Iron(II)Oxide, Aluminium(III)oxide are used to remove silica/silicon(IV)oxide as silicates which float above Lead preventing its reoxidation back to Lead(II)Oxide.
It is condensed in a spray of molten lead to prevent reoxidation to Zinc oxide. On further cooling , Zinc collects on the surface from where it can be tapped off (ii)Lead is a liquid and is ale to trickle to the bottom of the furnace from where it is tapped off. Quicklime/CaO, Iron(II)Oxide, Aluminium(III)oxide are used to remove silica/silicon(IV)oxide as silicates which float above Lead preventing its reoxidation back to Lead(II)Oxide. CaO(s) + SiO2(s) CaSiO3(s/l) (Slag-Calcium silicate) FeO(s) + SiO2(s) FeSiO3(s/l) (Slag-Iron silicate) Al2O3(s) + SiO2(s) Al2SiO4(s/l) (Slag-Aluminium silicate) c)Flow chart on extraction of Zinc from Calamine ,Zinc blende. Zinc ore (calamine /Zinc blende Powdered ore Froth flotation Roasting chamber Oil Water CO2 from calamine SO2 from Zinc blende Reduction chamber Iron/aluminium/ Limestone Coke Slag (Iron silicate/ aluminium silicate/calcium Condenser Filtration Gl ikWater
28 d) Flow chart on extraction of Lead from Galena e) Uses of Lead Lead is used in: (i)making gun-burettes. (ii)making protective clothes against nuclear (alpha rays/particle) radiation in a nuclear reactor. (iii)Mixed with tin(Sn) to make solder alloy f) Uses of Zinc Zinc is used in: Lead ore/Galena Powdered ore Froth flotation Roasting chamber oil Water Reduction chamber Iron/Limestone coke SO2(g) Slag(Iron silicate) Condenser Filtration LEAD VAPOUR Zinc residue
29 (i)Galvanization-when iron sheet is dipped in molten Zinc ,a thin layer of Zinc is formed on the surface.Since Zinc is more reactive than iron ,it reacts with elements of air(CO2/ O2 / H2O) to form basic Zinc carbonate(ZnCO3.Zn(OH)2).This sacrificial method protects iron from corrosion/rusting. (ii)As negative terminal and casing in dry/Laclanche cells. (iii)Making brass alloy with copper(Cu/Zn) g) Environmental effects of extracting Zinc and Lead.
(iii)Mixed with tin(Sn) to make solder alloy f) Uses of Zinc Zinc is used in: Lead ore/Galena Powdered ore Froth flotation Roasting chamber oil Water Reduction chamber Iron/Limestone coke SO2(g) Slag(Iron silicate) Condenser Filtration LEAD VAPOUR Zinc residue
29 (i)Galvanization-when iron sheet is dipped in molten Zinc ,a thin layer of Zinc is formed on the surface.Since Zinc is more reactive than iron ,it reacts with elements of air(CO2/ O2 / H2O) to form basic Zinc carbonate(ZnCO3.Zn(OH)2).This sacrificial method protects iron from corrosion/rusting. (ii)As negative terminal and casing in dry/Laclanche cells. (iii)Making brass alloy with copper(Cu/Zn) g) Environmental effects of extracting Zinc and Lead. (i) Lead and Lead salts are carcinogenic/causes cancer (ii)Carbon(IV)oxide is a green house gas that causes/accelerate global warming. (iii)Carbon(II)oxide is a colourless odourless poisonous /toxic gas that combines with haemoglobin in the blood to form stable carboxyhaemoglobin reducing free haemoglobin leading to death. (iv) Sulphur(IV)oxide is a gas that has a pungent poisonous smell that causes headache to human if in high concentration. (v)Any leakages in Sulphur(IV)oxide gas escapes to the water bodies to form weak sulphuric(VI)acid lowering the pH of the water. This causes marine pollution /death of aquatic life, accelerated rusting/corrosion of metals/roofs and breathing problems to human beings. h) Test for presence of Zinc/ Lead. If an ore is suspected to contain Zinc/Lead it is: I.added hot concentrated Nitric(V)acid to free the ions present. Note: Concentrated Sulphuric(VI)acid forms insoluble PbSO4 thus cannot be used to free the ions in Lead salts. II.the free ions are then added a precipitating reagent mostly 2M sodium hydroxide or 2M aqueous ammonia with the formation of; (i)a soluble precipitate in excess of 2M sodium hydroxide if Zn2+, Pb2+, Al3+ions are present.
If an ore is suspected to contain Zinc/Lead it is: I.added hot concentrated Nitric(V)acid to free the ions present. Note: Concentrated Sulphuric(VI)acid forms insoluble PbSO4 thus cannot be used to free the ions in Lead salts. II.the free ions are then added a precipitating reagent mostly 2M sodium hydroxide or 2M aqueous ammonia with the formation of; (i)a soluble precipitate in excess of 2M sodium hydroxide if Zn2+, Pb2+, Al3+ions are present. (ii)a white precipitate that dissolves to form a colorless solution in excess 2M aqueous ammonia if Zn2+ions are present. (iii)an insoluble white precipitate in excess 2M aqueous ammonia if Pb2+, Al3+ions are present. (iv) Pb2+ ions form a white precipitate when any soluble SO42-, SO32-, CO32-, Cl-, is added while Al3+ ions do not form a white precipitate
30 (v) Pb2+ ions form a yellow precipitate when any soluble I-(e.g. Potassium/sodium Iodide) is added while Al3+ ions do not form a yellow precipitate. (vi) Pb2+ ions form a black precipitate when any soluble S-(e.g.