JK-TK/Newdata huggingface dataset:
(ii)Deliquescent salts /compounds are those that absorb water from the atmosphere and form a solution. Some salts which are deliquescent include: Sodium nitrate(V),Calcium chloride, Sodium hydroxide, Iron(II)chloride, Magnesium chloride. (iii)Efflorescent salts/compounds are those that lose their water of crystallization to the atmosphere. Some salts which effloresces include: sodium carbonate decahydrate, Iron(II)sulphate(VI)heptahydrate, sodium sulphate (VI)decahydrate. (e)Some salts contain water of crystallization.They are hydrated.Others do not contain water of crystallization. They are anhydrous. Table showing some hydrated salts. Name of hydrated salt Chemical formula Copper(II)sulphate(VI)pentahydrate CuSO4.5H2O Aluminium(III)sulphate(VI)hexahydrate Al2 (SO4) 3.6H2O Zinc(II)sulphate(VI)heptahydrate ZnSO4.7H2O Iron(II)sulphate(VI)heptahydrate FeSO4.7H2O Calcium(II)sulphate(VI)heptahydrate CaSO4.7H2O Magnesium(II)sulphate(VI)heptahydrate MgSO4.7H2O Sodium sulphate(VI)decahydrate Na2SO4.10H2O Sodium carbonate(IV)decahydrate Na2CO3.10H2O Potassium carbonate(IV)decahydrate K2CO3.10H2O Potassium sulphate(VI)decahydrate K2SO4.10H2O (f)Some salts exist as a simple salt while some as complex salts. Below are some complex salts.
Table showing some hydrated salts. Name of hydrated salt Chemical formula Copper(II)sulphate(VI)pentahydrate CuSO4.5H2O Aluminium(III)sulphate(VI)hexahydrate Al2 (SO4) 3.6H2O Zinc(II)sulphate(VI)heptahydrate ZnSO4.7H2O Iron(II)sulphate(VI)heptahydrate FeSO4.7H2O Calcium(II)sulphate(VI)heptahydrate CaSO4.7H2O Magnesium(II)sulphate(VI)heptahydrate MgSO4.7H2O Sodium sulphate(VI)decahydrate Na2SO4.10H2O Sodium carbonate(IV)decahydrate Na2CO3.10H2O Potassium carbonate(IV)decahydrate K2CO3.10H2O Potassium sulphate(VI)decahydrate K2SO4.10H2O (f)Some salts exist as a simple salt while some as complex salts. Below are some complex salts. Table of some complex salts Name of complex salt Chemical formula Colour of the complex salt Tetraamminecopper(II)sulphate(VI) Cu(NH3) 4 SO4 H2O Royal/deep blue solution
Tetraamminezinc(II)nitrate(V) Zn(NH3) 4 (NO3 )2 Colourless solution Tetraamminecopper(II) nitrate(V) Cu(NH3) 4 (NO3 )2 Royal/deep blue solution Tetraamminezinc(II)sulphate(VI) Zn(NH3) 4 SO4 Colourless solution (g)Some salts exist as two salts in one. They are called double salts.
Below are some complex salts. Table of some complex salts Name of complex salt Chemical formula Colour of the complex salt Tetraamminecopper(II)sulphate(VI) Cu(NH3) 4 SO4 H2O Royal/deep blue solution
Tetraamminezinc(II)nitrate(V) Zn(NH3) 4 (NO3 )2 Colourless solution Tetraamminecopper(II) nitrate(V) Cu(NH3) 4 (NO3 )2 Royal/deep blue solution Tetraamminezinc(II)sulphate(VI) Zn(NH3) 4 SO4 Colourless solution (g)Some salts exist as two salts in one. They are called double salts. Table of some double salts Name of double salts Chemical formula Trona(sodium sesquicarbonate) Na2CO3 NaHCO3.2H2O Ammonium iron(II)sulphate(VI) FeSO4(NH4) 2SO4.2H2O Ammonium aluminium(III)sulphate(VI) Al2(SO4) 3(NH4) 2SO4.H2O (h)Some salts dissolve in water to form a solution. They are said to be soluble. Others do not dissolve in water. They form a suspension/precipitate in water.
They are said to be soluble. Others do not dissolve in water. They form a suspension/precipitate in water. Table of solubility of salts Soluble salts Insoluble salts All nitrate(V)salts All sulphate(VI)/SO42- salts except Barium(II) sulphate(VI)/BaSO4 Calcium(II) sulphate(VI)/CaSO4 Lead(II) sulphate(VI)/PbSO4 All sulphate(IV)/SO32- salts except Barium(II) sulphate(IV)/BaSO3 Calcium(II) sulphate(IV)/CaSO3 Lead(II) sulphate(IV)/PbSO3 All chlorides/Cl- except Silver chloride/AgCl Lead(II)chloride/PbCl2(dissolves in hot water) All phosphate(V)/PO43- All sodium,potassium and ammonium salts All hydrogen carbonates/HCO3- All hydrogen sulphate(VI)/ HSO4- Sodium carbonate/Na2CO3, potassium carbonate/ K2CO3, ammonium carbonate (NH4) 2CO3 except All carbonates All alkalis(KOH,NaOH, NH4OH) except All bases 13 Salts can be prepared in a school laboratory by a method that uses its solubility in water. (a) Soluble salts may be prepared by using any of the following methods: (i)Direct displacement/reaction of a metal with an acid. By reacting a metal higher in the reactivity series than hydrogen with a dilute acid,a salt is formed and hydrogen gas is evolved. Excess of the metal must be used to ensure all the acid has reacted. When effervescence/bubbling /fizzing has stopped ,excess metal is filtered. The filtrate is heated to concentrate then allowed to crystallize. Washing with distilled water then drying between filter papers produces a sample crystal of the salt. i.e.
The filtrate is heated to concentrate then allowed to crystallize. Washing with distilled water then drying between filter papers produces a sample crystal of the salt. i.e. M(s) + H2X -> MX(aq) + H2(g) Examples Mg(s) + H2SO4(aq) -> MgSO4 (aq) + H2(g) Zn(s) + H2SO4(aq) -> ZnSO4 (aq) + H2(g) Pb(s) + 2HNO3(aq) -> Pb(NO3) 2(aq) + H2(g) Ca(s) + 2HNO3(aq) -> Ca(NO3) 2(aq) + H2(g) Mg(s) + 2HNO3(aq) -> Mg(NO3) 2(aq) + H2(g) Mg(s) + 2HCl(aq) -> MgCl 2(aq) + H2(g) Zn(s) + 2HCl(aq) -> ZnCl 2(aq) + H2(g) (ii)Reaction of an insoluble base with an acid By adding an insoluble base (oxide/hydroxide )to a dilute acid until no more dissolves, in the acid,a salt and water are formed. Excess of the base is filtered off. The filtrate is heated to concentrate ,allowed to crystallize then washed with distilled water before drying between filter papers e.g.
M(s) + H2X -> MX(aq) + H2(g) Examples Mg(s) + H2SO4(aq) -> MgSO4 (aq) + H2(g) Zn(s) + H2SO4(aq) -> ZnSO4 (aq) + H2(g) Pb(s) + 2HNO3(aq) -> Pb(NO3) 2(aq) + H2(g) Ca(s) + 2HNO3(aq) -> Ca(NO3) 2(aq) + H2(g) Mg(s) + 2HNO3(aq) -> Mg(NO3) 2(aq) + H2(g) Mg(s) + 2HCl(aq) -> MgCl 2(aq) + H2(g) Zn(s) + 2HCl(aq) -> ZnCl 2(aq) + H2(g) (ii)Reaction of an insoluble base with an acid By adding an insoluble base (oxide/hydroxide )to a dilute acid until no more dissolves, in the acid,a salt and water are formed. Excess of the base is filtered off. The filtrate is heated to concentrate ,allowed to crystallize then washed with distilled water before drying between filter papers e.g. PbO(s) + 2HNO3(aq) -> Pb(NO3) 2(aq) + H2O (l) Pb(OH)2(s) + 2HNO3(aq) -> Pb(NO3) 2(aq) + 2H2O (l) CaO (s) + 2HNO3(aq) -> Ca(NO3) 2(aq) + H2O (l) MgO (s) + 2HNO3(aq) -> Mg(NO3) 2(aq) + H2O (l) MgO (s) + 2HCl(aq) -> MgCl 2(aq) + H2O (l) ZnO (s) + 2HCl(aq) -> ZnCl 2(aq) + H2O (l) Zn(OH)2(s) + 2HNO3(aq) -> Zn(NO3) 2(aq) + 2H2O (l) CuO (s) + 2HCl(aq) -> CuCl 2(aq) + H2O (l) CuO (s) + H2SO4(aq) -> CuSO4(aq) + H2O (l) Ag2O(s) + 2HNO3(aq) -> 2AgNO3(aq) + H2O (l) Na2O(s) + 2HNO3(aq) -> 2NaNO3(aq) + H2O (l) (iii)reaction of insoluble /soluble carbonate /hydrogen carbonate with an acid.
Excess of the base is filtered off. The filtrate is heated to concentrate ,allowed to crystallize then washed with distilled water before drying between filter papers e.g. PbO(s) + 2HNO3(aq) -> Pb(NO3) 2(aq) + H2O (l) Pb(OH)2(s) + 2HNO3(aq) -> Pb(NO3) 2(aq) + 2H2O (l) CaO (s) + 2HNO3(aq) -> Ca(NO3) 2(aq) + H2O (l) MgO (s) + 2HNO3(aq) -> Mg(NO3) 2(aq) + H2O (l) MgO (s) + 2HCl(aq) -> MgCl 2(aq) + H2O (l) ZnO (s) + 2HCl(aq) -> ZnCl 2(aq) + H2O (l) Zn(OH)2(s) + 2HNO3(aq) -> Zn(NO3) 2(aq) + 2H2O (l) CuO (s) + 2HCl(aq) -> CuCl 2(aq) + H2O (l) CuO (s) + H2SO4(aq) -> CuSO4(aq) + H2O (l) Ag2O(s) + 2HNO3(aq) -> 2AgNO3(aq) + H2O (l) Na2O(s) + 2HNO3(aq) -> 2NaNO3(aq) + H2O (l) (iii)reaction of insoluble /soluble carbonate /hydrogen carbonate with an acid. By adding an excess of a soluble /insoluble carbonate or hydrogen carbonate to adilute acid, effervescence /fizzing/bubbling out of carbon(IV)oxide gas shows the
reaction is taking place. When effervescence /fizzing/bubbling out of the gas is over, excess of the insoluble carbonate is filtered off. The filtrate is heated to concentrate ,allowed to crystallize then washed with distilled water before drying between filter paper papers e.g.
By adding an excess of a soluble /insoluble carbonate or hydrogen carbonate to adilute acid, effervescence /fizzing/bubbling out of carbon(IV)oxide gas shows the
reaction is taking place. When effervescence /fizzing/bubbling out of the gas is over, excess of the insoluble carbonate is filtered off. The filtrate is heated to concentrate ,allowed to crystallize then washed with distilled water before drying between filter paper papers e.g. PbCO3 (s) + 2HNO3(aq) -> Pb(NO3) 2(aq) + H2O (l)+ CO2(g) ZnCO3 (s) + 2HNO3(aq) -> Zn(NO3) 2(aq) + H2O (l)+ CO2(g) CaCO3 (s) + 2HNO3(aq) -> Ca(NO3) 2(aq) + H2O (l)+ CO2(g) MgCO3 (s) + H2SO4(aq) -> MgSO4(aq) + H2O (l)+ CO2(g) Cu CO3 (s) + H2SO4(aq) -> CuSO4(aq) + H2O (l) + CO2(g) Ag2CO3 (s) + 2HNO3(aq) -> 2AgNO3(aq) + H2O (l) + CO2(g) Na2CO3 (s) + 2HNO3(aq) -> 2NaNO3(aq) + H2O (l) + CO2(g) K2CO3 (s) + 2HCl(aq) -> 2KCl(aq) + H2O (l) + CO2(g) NaHCO3 (s) + HNO3(aq) -> NaNO3(aq) + H2O (l) + CO2(g) KHCO3 (s) + HCl(aq) -> KCl(aq) + H2O (l) + CO2(g) (iv)neutralization/reaction of soluble base/alkali with dilute acid By adding an acid to a burette into a known volume of an alkali with 2-3 drops of an indicator, the colour of the indicator changes when the acid has completely reacted with an alkali at the end point.
When effervescence /fizzing/bubbling out of the gas is over, excess of the insoluble carbonate is filtered off. The filtrate is heated to concentrate ,allowed to crystallize then washed with distilled water before drying between filter paper papers e.g. PbCO3 (s) + 2HNO3(aq) -> Pb(NO3) 2(aq) + H2O (l)+ CO2(g) ZnCO3 (s) + 2HNO3(aq) -> Zn(NO3) 2(aq) + H2O (l)+ CO2(g) CaCO3 (s) + 2HNO3(aq) -> Ca(NO3) 2(aq) + H2O (l)+ CO2(g) MgCO3 (s) + H2SO4(aq) -> MgSO4(aq) + H2O (l)+ CO2(g) Cu CO3 (s) + H2SO4(aq) -> CuSO4(aq) + H2O (l) + CO2(g) Ag2CO3 (s) + 2HNO3(aq) -> 2AgNO3(aq) + H2O (l) + CO2(g) Na2CO3 (s) + 2HNO3(aq) -> 2NaNO3(aq) + H2O (l) + CO2(g) K2CO3 (s) + 2HCl(aq) -> 2KCl(aq) + H2O (l) + CO2(g) NaHCO3 (s) + HNO3(aq) -> NaNO3(aq) + H2O (l) + CO2(g) KHCO3 (s) + HCl(aq) -> KCl(aq) + H2O (l) + CO2(g) (iv)neutralization/reaction of soluble base/alkali with dilute acid By adding an acid to a burette into a known volume of an alkali with 2-3 drops of an indicator, the colour of the indicator changes when the acid has completely reacted with an alkali at the end point. The procedure is then repeated without the indicator .The solution mixture is then heated to concentrate , allowed to crystallize ,washed with distilled water before drying with filter papers. e.g.
PbCO3 (s) + 2HNO3(aq) -> Pb(NO3) 2(aq) + H2O (l)+ CO2(g) ZnCO3 (s) + 2HNO3(aq) -> Zn(NO3) 2(aq) + H2O (l)+ CO2(g) CaCO3 (s) + 2HNO3(aq) -> Ca(NO3) 2(aq) + H2O (l)+ CO2(g) MgCO3 (s) + H2SO4(aq) -> MgSO4(aq) + H2O (l)+ CO2(g) Cu CO3 (s) + H2SO4(aq) -> CuSO4(aq) + H2O (l) + CO2(g) Ag2CO3 (s) + 2HNO3(aq) -> 2AgNO3(aq) + H2O (l) + CO2(g) Na2CO3 (s) + 2HNO3(aq) -> 2NaNO3(aq) + H2O (l) + CO2(g) K2CO3 (s) + 2HCl(aq) -> 2KCl(aq) + H2O (l) + CO2(g) NaHCO3 (s) + HNO3(aq) -> NaNO3(aq) + H2O (l) + CO2(g) KHCO3 (s) + HCl(aq) -> KCl(aq) + H2O (l) + CO2(g) (iv)neutralization/reaction of soluble base/alkali with dilute acid By adding an acid to a burette into a known volume of an alkali with 2-3 drops of an indicator, the colour of the indicator changes when the acid has completely reacted with an alkali at the end point. The procedure is then repeated without the indicator .The solution mixture is then heated to concentrate , allowed to crystallize ,washed with distilled water before drying with filter papers. e.g. NaOH (aq) + HNO3(aq) -> NaNO3(aq) + H2O (l) KOH (aq) + HNO3(aq) -> KNO3(aq) + H2O (l) KOH (aq) + HCl(aq) -> KCl(aq) + H2O (l) 2KOH (aq) + H2SO4(aq) -> K2SO4(aq) + 2H2O (l) 2 NH4OH (aq) + H2SO4(aq) -> (NH4)2SO4(aq) + 2H2O (l) NH4OH (aq) + HNO3(aq) -> NH4NO3(aq) + H2O (l) (iv)direct synthesis/combination.
The procedure is then repeated without the indicator .The solution mixture is then heated to concentrate , allowed to crystallize ,washed with distilled water before drying with filter papers. e.g. NaOH (aq) + HNO3(aq) -> NaNO3(aq) + H2O (l) KOH (aq) + HNO3(aq) -> KNO3(aq) + H2O (l) KOH (aq) + HCl(aq) -> KCl(aq) + H2O (l) 2KOH (aq) + H2SO4(aq) -> K2SO4(aq) + 2H2O (l) 2 NH4OH (aq) + H2SO4(aq) -> (NH4)2SO4(aq) + 2H2O (l) NH4OH (aq) + HNO3(aq) -> NH4NO3(aq) + H2O (l) (iv)direct synthesis/combination. When a metal burn in a gas jar containing a non metal , the two directly combine to form a salt. e.g. 2Na(s) + Cl2(g) -> 2NaCl(s) 2K(s) + Cl2(g) -> 2KCl(s) Mg(s) + Cl2(g) -> Mg Cl2 (s) Ca(s) + Cl2(g) -> Ca Cl2 (s) Some salts once formed undergo sublimation and hydrolysis. Care should be taken to avoid water/moisture into the reaction flask during their preparation.Such salts include aluminium(III)chloride(AlCl3) and iron (III)chloride(FeCl3)
1. Heated aluminium foil reacts with chlorine to form aluminium(III)chloride that sublimes away from the source of heating then deposited as solid again 2Al(s) + 3Cl2(g) -> 2AlCl3 (s/g) Once formed aluminium(III)chloride hydrolyses/reacts with water vapour / moisture present to form aluminium hydroxide solution and highly acidic fumes of hydrogen chloride gas. AlCl3(s)+ 3H2 O(g) -> Al(OH)3 (aq) + 3HCl(g) 2.
Care should be taken to avoid water/moisture into the reaction flask during their preparation.Such salts include aluminium(III)chloride(AlCl3) and iron (III)chloride(FeCl3)
1. Heated aluminium foil reacts with chlorine to form aluminium(III)chloride that sublimes away from the source of heating then deposited as solid again 2Al(s) + 3Cl2(g) -> 2AlCl3 (s/g) Once formed aluminium(III)chloride hydrolyses/reacts with water vapour / moisture present to form aluminium hydroxide solution and highly acidic fumes of hydrogen chloride gas. AlCl3(s)+ 3H2 O(g) -> Al(OH)3 (aq) + 3HCl(g) 2. Heated iron filings reacts with chlorine to form iron(III)chloride that sublimes away from the source of heating then deposited as solid again 2Fe(s) + 3Cl2(g) -> 2FeCl3 (s/g) Once formed , aluminium(III)chloride hydrolyses/reacts with water vapour / moisture present to form aluminium hydroxide solution and highly acidic fumes of hydrogen chloride gas. FeCl3(s)+ 3H2 O(g) -> Fe(OH)3 (aq) + 3HCl(g) (b)Insoluble salts can be prepared by reacting two suitable soluble salts to form one soluble and one insoluble. This is called double decomposition or precipitation. The mixture is filtered and the residue is washed with distilled water then dried.
FeCl3(s)+ 3H2 O(g) -> Fe(OH)3 (aq) + 3HCl(g) (b)Insoluble salts can be prepared by reacting two suitable soluble salts to form one soluble and one insoluble. This is called double decomposition or precipitation. The mixture is filtered and the residue is washed with distilled water then dried. CuSO4(aq) + Na2CO3 (aq) -> CuCO3 (s) + Na2 SO4(aq) BaCl2(aq) + K2SO4 (aq) -> BaSO4 (s) + 2KCl (aq) Pb(NO3)2(aq) + K2SO4 (aq) -> PbSO4 (s) + 2KNO3 (aq) 2AgNO3(aq) + MgCl2 (aq) -> 2AgCl(s) + Mg(NO3)2 (aq) Pb(NO3)2(aq) + (NH4) 2SO4 (aq) -> PbSO4 (s) + 2NH4NO 3(aq) BaCl2(aq) + K2SO3 (aq) -> BaSO3 (s) + 2KCl (aq) 14. Salts may lose their water of crystallization , decompose ,melt or sublime on heating on a Bunsen burner flame. The following shows the behavior of some salts on heating gently /or strongly in a laboratory school burner: (a)effect of heat on chlorides All chlorides have very high melting and boiling points and therefore are not affected by laboratory heating except ammonium chloride. Ammonium chloride sublimes on gentle heating. It dissociate into the constituent ammonia and hydrogen chloride gases on strong heating. NH4Cl(s) NH4Cl(g) NH3(g) + HCl(g) (sublimation) (dissociation) (b)effect of heat on nitrate(V) (i) Potassium nitrate(V)/KNO3 and sodium nitrate(V)/NaNO3 decompose on heating to form Potassium nitrate(III)/KNO2 and sodium nitrate(III)/NaNO2 and producing Oxygen gas in each case.
Ammonium chloride sublimes on gentle heating. It dissociate into the constituent ammonia and hydrogen chloride gases on strong heating. NH4Cl(s) NH4Cl(g) NH3(g) + HCl(g) (sublimation) (dissociation) (b)effect of heat on nitrate(V) (i) Potassium nitrate(V)/KNO3 and sodium nitrate(V)/NaNO3 decompose on heating to form Potassium nitrate(III)/KNO2 and sodium nitrate(III)/NaNO2 and producing Oxygen gas in each case. 2KNO3 (s) -> 2KNO2(s) + O2(g) 2NaNO3 (s) -> 2NaNO2(s) + O2(g) (ii)Heavy metal nitrates(V) salts decompose on heating to form the oxide and a mixture of brown acidic nitrogen(IV)oxide and oxygen gases. e.g. 2Ca(NO3)2 (s) -> 2CaO(s) + 4NO2(g) + O2(g) 2Mg(NO3)2(s) -> 2MgO(s) + 4NO2(g) + O2(g) 2Zn(NO3)2(s) -> 2ZnO(s) + 4NO2(g) + O2(g) 2Pb(NO3)2(s) -> 2PbO(s) + 4NO2(g) + O2(g) 2Cu(NO3)2(s) -> 2CuO(s) + 4NO2(g) + O2(g) 2Fe(NO3)2(s) -> 2FeO(s) + 4NO2(g) + O2(g) (iii)Silver(I)nitrate(V) and mercury(II) nitrate(V) are lowest in the reactivity series. They decompose on heating to form the metal(silver and mercury)and the Nitrogen(IV)oxide and oxygen gas. i.e.
2Ca(NO3)2 (s) -> 2CaO(s) + 4NO2(g) + O2(g) 2Mg(NO3)2(s) -> 2MgO(s) + 4NO2(g) + O2(g) 2Zn(NO3)2(s) -> 2ZnO(s) + 4NO2(g) + O2(g) 2Pb(NO3)2(s) -> 2PbO(s) + 4NO2(g) + O2(g) 2Cu(NO3)2(s) -> 2CuO(s) + 4NO2(g) + O2(g) 2Fe(NO3)2(s) -> 2FeO(s) + 4NO2(g) + O2(g) (iii)Silver(I)nitrate(V) and mercury(II) nitrate(V) are lowest in the reactivity series. They decompose on heating to form the metal(silver and mercury)and the Nitrogen(IV)oxide and oxygen gas. i.e. 2AgNO3(s) -> 2Ag (s) + 2NO2(g) + O2(g) 2Hg(NO3)2 (s) -> 2Hg (s) + 4NO2(g) + O2(g) (iv)Ammonium nitrate(V) and Ammonium nitrate(III) decompose on heating to Nitrogen(I)oxide(relights/rekindles glowing splint) and nitrogen gas respectively.Water is also formed.i.e. NH4NO3(s) -> N2O (g) + H2O(l) NH4NO2(s) -> N2 (g) + H2O(l) (c) effect of heat on nitrate(V) Only Iron(II)sulphate(VI), Iron(III)sulphate(VI) and copper(II)sulphate(VI) decompose on heating. They form the oxide, and produce highly acidic fumes of acidic sulphur(IV)oxide gas.
2AgNO3(s) -> 2Ag (s) + 2NO2(g) + O2(g) 2Hg(NO3)2 (s) -> 2Hg (s) + 4NO2(g) + O2(g) (iv)Ammonium nitrate(V) and Ammonium nitrate(III) decompose on heating to Nitrogen(I)oxide(relights/rekindles glowing splint) and nitrogen gas respectively.Water is also formed.i.e. NH4NO3(s) -> N2O (g) + H2O(l) NH4NO2(s) -> N2 (g) + H2O(l) (c) effect of heat on nitrate(V) Only Iron(II)sulphate(VI), Iron(III)sulphate(VI) and copper(II)sulphate(VI) decompose on heating. They form the oxide, and produce highly acidic fumes of acidic sulphur(IV)oxide gas. 2FeSO4 (s) -> Fe2O3(s) + SO3(g) + SO2(g) Fe2(SO4) 3(s) -> Fe2O3(s) + SO3(g) CuSO4 (s) -> CuO(s) + SO3(g)
(d) effect of heat on carbonates(IV) and hydrogen carbonate(IV). (i)Sodium carbonate(IV)and potassium carbonate(IV)do not decompose on heating. (ii)Heavy metal nitrate(IV)salts decompose on heating to form the oxide and produce carbon(IV)oxide gas. Carbon (IV)oxide gas forms a white precipitate when bubbled in lime water. The white precipitate dissolves if the gas is in excess. e.g. CuCO3 (s) -> CuO(s) + CO2(g) CaCO3 (s) -> CaO(s) + CO2(g) PbCO3 (s) -> PbO(s) + CO2(g) FeCO3 (s) -> FeO(s) + CO2(g) ZnCO3 (s) -> ZnO(s) + CO2(g) (iii)Sodium hydrogen carbonate(IV) and Potassium hydrogen carbonate(IV)decompose on heating to give the corresponding carbonate (IV) and form water and carbon(IV)oxide gas. i.e.
e.g. CuCO3 (s) -> CuO(s) + CO2(g) CaCO3 (s) -> CaO(s) + CO2(g) PbCO3 (s) -> PbO(s) + CO2(g) FeCO3 (s) -> FeO(s) + CO2(g) ZnCO3 (s) -> ZnO(s) + CO2(g) (iii)Sodium hydrogen carbonate(IV) and Potassium hydrogen carbonate(IV)decompose on heating to give the corresponding carbonate (IV) and form water and carbon(IV)oxide gas. i.e. 2NaHCO 3(s) -> Na2CO3(s) + CO2(g) + H2O(l) 2KHCO 3(s) -> K2CO3(s) + CO2(g) + H2O(l) (iii) Calcium hydrogen carbonate (IV) and Magnesium hydrogen carbonate(IV) decompose on heating to give the corresponding carbonate (IV) and form water and carbon(IV)oxide gas. i. e. Ca(HCO3) 2(aq) -> CaCO3(s) + CO2(g) + H2O(l) Mg(HCO3) 2(aq) -> MgCO3(s) + CO2(g) + H2O(l)
1 INTRODUCTION TO ELECTROLYSIS (ELECTROLYTIC CELL) 1.Electrolysis is defined simply as the decomposition of a compound by an electric current/electricity. A compound that is decomposed by an electric current is called an electrolyte. Some electrolytes are weak while others are strong. 2.Strong electrolytes are those that are fully ionized/dissociated into (many) ions. Common strong electrolytes include: (i)all mineral acids (ii)all strong alkalis/sodium hydroxide/potassium hydroxide. (iii)all soluble salts 3.Weak electrolytes are those that are partially/partly ionized/dissociated into (few) ions. Common weak electrolytes include: (i)all organic acids (ii)all bases except sodium hydroxide/potassium hydroxide. (iii)Water 4. A compound that is not decomposed by an electric current is called nonelectrolyte.
Common weak electrolytes include: (i)all organic acids (ii)all bases except sodium hydroxide/potassium hydroxide. (iii)Water 4. A compound that is not decomposed by an electric current is called nonelectrolyte. Non-electrolytes are those compounds /substances that exist as molecules and thus cannot ionize/dissociate into(any) ions . Common non-electrolytes include: (i) most organic solvents (e.g. petrol/paraffin/benzene/methylbenzene/ethanol) (ii)all hydrocarbons(alkanes /alkenes/alkynes) (iii)Chemicals of life(e.g. proteins, carbohydrates, lipids, starch, sugar) 5. An electrolytes in solid state have fused /joined ions and therefore do not conduct electricity but the ions (cations and anions) are free and mobile in molten and aqueous (solution, dissolved in water) state. 6.During electrolysis, the free ions are attracted to the electrodes. An electrode is a rod through which current enter and leave the electrolyte during electrolysis. 2 An electrode that does not influence/alter the products of electrolysis is called an inert electrode. Common inert electrodes include: (i)Platinum (ii)Carbon graphite Platinum is not usually used in a school laboratory because it is very expensive. Carbon graphite is easily/readily and cheaply available (from used dry cells). 7.The positive electrode is called Anode.The anode is the electrode through which current enter the electrolyte/electrons leave the electrolyte 8.The negative electrode is called Cathode. The cathode is the electrode through which current leave the electrolyte / electrons enter the electrolyte 9. During the electrolysis, free anions are attracted to the anode where they lose /donate electrons to form neutral atoms/molecules. i.e. M(l) -> M+(l) + e (for cations from molten electrolytes) M(s) -> M+(aq) + e (for cations from electrolytes in aqueous state / solution / dissolved in water) The neutral atoms /molecules form the products of electrolysis at the anode. This is called discharge at anode 10. During electrolysis, free cations are attracted to the cathode where they gain /accept/acquire electrons to form neutral atoms/molecules.