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INTRODUCTION TO SALTS

1.(a) A salt is an ionic compound formed when the cation from a base combine with the anion derived from an acid.

A salt is therefore formed when the hydrogen ions in an acid are replaced wholly/fully or partially/partly, directly or indirectly by a metal or ammonium radical.

(b) The number of ionizable/replaceable hydrogen in an acid is called basicity of an acid.

Some acids are therefore:

(i)monobasic acids generally denoted HX e.g.

HCl, HNO3,HCOOH,CH3COOH.

(ii)dibasic acids generally denoted H2X e.g.

H2SO4, H2SO3, H2CO3,HOOCOOH.

(iii)tribasic acids generally denoted H3X e.g.

H3PO4.

(c) Some salts are normal salts while others are acid salts.

(i)A normal salt is formed when all the ionizable /replaceable hydrogen in an acid is replaced by a metal or metallic /ammonium radical.

(ii)An acid salt is formed when part/portion the ionizable /replaceable hydrogen in an acid is replaced by a metal or metallic /ammonium radical.

Table showing normal and acid salts derived from common acids

Acid name

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Chemical formula

Basicity

Normal salt

Acid salt

Hydrochloric acid

HCl

Monobasic

Chloride(Cl)

None

Nitric(V)acid

HNO3

Monobasic

Nitrate(V)(NO3)

None

Nitric(III)acid

HNO2

Monobasic

Nitrate(III)(NO2)

None

Sulphuric(VI)acid

H2SO4

Dibasic

Sulphate(VI) (SO42-)

Hydrogen sulphate(VI)

(HSO4)

Sulphuric(IV)acid

H2SO3

Dibasic

Sulphate(IV) (SO32-)

Hydrogen sulphate(IV)

(HSO3)

Carbonic(IV)acid

H2CO3

Dibasic

Carbonate(IV)(CO32-)

Hydrogen carbonate(IV)

(HCO3)

Phosphoric(V)

acid

H3PO4

Tribasic

Phosphate(V)(PO43-)

Dihydrogen phosphate(V)

(H2PO42-)

 

Hydrogen diphosphate(V)

(HP2O42-)

The table below show shows some examples of salts.

Base/alkali

Cation

Acid

Anion

Salt

Chemical name of salts

NaOH

Na+

HCl

Cl

NaCl

Sodium(I)chloride

Mg(OH)2

Mg2+

H2SO4

SO42-

MgSO4

Mg(HSO4)2

Magnesium sulphate(VI)

Magnesium hydrogen sulphate(VI)

Pb(OH)2

Pb2+

HNO3

NO3

Pb(NO3)2

Lead(II)nitrate(V)

Ba(OH)2

Ba2+

HNO3

NO3

Ba(NO3)2

Barium(II)nitrate(V)

Ca(OH)2

Ba2+

H2SO4

SO42-

MgSO4

Calcium sulphate(VI)

NH4OH

NH4+

H3PO4

PO43-

(NH4 )3PO4

(NH4 )2HPO4

NH4 H2PO4

Ammonium phosphate(V)

Diammonium phosphate(V)

Ammonium diphosphate(V)

KOH

K+

H3PO4

PO43-

K3PO4

Potassium phosphate(V)

Al(OH)3

Al3+

H2SO4

SO42-

Al2(SO4)2

Aluminium(III)sulphate(VI)

Fe(OH)2

Fe2+

H2SO4

SO42-

FeSO4

Iron(II)sulphate(VI)

Fe(OH)3

Fe3+

H2SO4

SO42-

Fe2(SO4)2

Iron(III)sulphate(VI)

 

(d) Some salts undergo hygroscopy, deliquescence and efflorescence.

(i) Hygroscopic salts /compounds are those that absorb water from the atmosphere but do not form a solution.

Some salts which are hygroscopic include anhydrous copper(II)sulphate(VI), anhydrous cobalt(II)chloride, potassium nitrate(V) common table salt.

(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 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.

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/Clexcept

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.

  1. 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.

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.

By adding an excess of a soluble /insoluble carbonate or hydrogen carbonate to a dilute 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. 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 aluminum (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.

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.

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.

 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.

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) –

 

Name…………………………………………….Class…………….Adm No….…..

CHEMISTRY Practice balancing Chemical equations

Date done………………..Date marked……………….Date revised……..…..

 

Balance the following chemical equations in the spaces provided on the question paper.

 

Ca (OH)2(aq) + Cl2(g) → CaCl2(aq) + CaOCl2(aq) + H2O(l)

(Cold/dilute) (Calcium Chlorate(I))

 

Ca (OH)2(aq) +Cl2(g) → CaCl2(aq) +Ca(ClO3)2(aq) +H2O(l)

(Hot/Concentrated) (Calcium Chlorate(V))

NaOH + Cl2(g) → NaClO3 (aq) + NaCl(aq) + 3H2O(l) (Sodium Chlorate (V)

KOH + Cl2(g) → KClO3 (aq)+ KCl(aq) + H2O(l) (Potassium Chlorate (V)

Ca (OH)2(aq)+ Cl2(g) → CaCl2(aq)+CaOCl2(aq)+ H2O(l)

(Cold/dilute) (Calcium Chlorate(I))

NaCl(s) + H2SO4(l) -> NaHSO4(aq) + HCl(g)

KCl(s) + H2SO4(l) -> KHSO4(aq) + HCl(g)

CaO(s) + 2H2O(l) -> Ca(OH)2(aq) + H2O(l)

Ca(OH)2(aq) + Cl2 (g) -> CaOCl2(aq) + H2O(l)

HCl(s) + NH3(g) -> NH4Cl(s)

Fe(s)  + 2HCl(aq) ->  FeCl2(aq + H2 (g)

Zn(s) + 2HCl(aq) ->  ZnCl2(aq + H2 (g)

Mg(s) + 2HCl(aq) ->  MgCl2(aq + H2 (g)

2Li(s) + 2HCl(aq) ->  2LiCl(aq + H2 (g)

Ca (OH)2(aq) +Cl2(g) → CaCl2(aq) +Ca(ClO3)2(aq) +H2O(l)

(Hot/Concentrated) (Calcium Chlorate(V))

CaCO3 (s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)

(Colourless solution)

1.Chemical equation:

Ionic equation:

CaCO3 (s)  + 2H+(aq) → Ca2+(aq) + H2O(l) + CO2(g)

2.Chemical equation:

Ag2CO3 (s) + 2HCl(aq) → 2AgCl(s) + H2O(l) + CO2(g)

  (Coats/Cover Ag2CO3)

3.Chemical equation:

NaHCO3 (s) + HCl(aq) → NaCl(aq) +H2O(l) +CO2(g)

  (colourless solution)

Ionic equation:

NaHCO3 (s) + H+(aq) → Na+(aq) + H2O(l)   + CO2(g)

4.Chemical equation:

CuCO3 (s) + 2HCl(aq) → CuCl2(aq)+ H2O(l) + CO2(g)

  (Blue Solution)

Ionic equation:

CuCO3 (s)  + 2H+(aq) →Cu2+(aq) + H2O(l)   + CO2(g)

5.Chemical equation:

FeCO3 (s) + 2HCl(aq) →FeCl2(aq)+ H2O(l) + CO2(g)

  (green solution)

Ionic equation:

FeCO3 (s)  + 2H+(aq) → Fe2+(aq) + H2O(l)+ CO2(g)

6.Chemical equation:

(NH4) 2CO3 (s)+2HCl(aq) →2NH4 Cl(aq)+H2O(l)+ CO2(g)

Ionic equation:

(NH4) 2CO3 (s)+2H+ (aq) →2NH4 + (aq)+H2O(l)+ CO2(g)

Chemical equation:

 NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Ionic equation:  

OH(aq)  +  H+(aq)  →  H2O(l)

Chemical equation:  

KOH(aq) + HCl(aq) → KCl(aq) + H2O(l)

Ionic equation:  

OH(aq)  +  H+(aq)  →  H2O(l)

Chemical equation:  

NH4OH(aq) + HCl(aq) → NH4Cl(aq) + H2O(l)

Ionic equation:  

OH(aq)  +  H+(aq)  →  H2O(l)

CuO(s) + 2HCl (aq) → CaCl2(aq) + H2O(l)

  Ionic equation:

CuO
(s)  + 2H+(aq) →  Cu2+(aq) + H2O(l)

 Chemical equation:

CaO(s) + HCl (aq) → CaCl2 (aq) + H2O (l)

  Ionic equation:

CuO
(s)  + 2H+(aq) →  Cu2+(aq) + H2O(l)

 Chemical equation:

PbO(s) + 2HCl (aq) → PbCl2 (s) + H2O (l)

  No ionic equation

  Chemical equation:

ZnO(s) + HCl (aq) → ZnCl2 (aq) + H2O (l)

Ionic equation:

ZnO
(s)  + 2H+(aq) →  Zn2+(aq) + H2O(l)

H2(g)   + Cl2(g) → 2HCl(g)

HCl(g) +   (aq)  →  HCl(aq)

NH4Cl(s) -> HCl(g) + NH3 (g)

 

 

 

 

 

Name ……………………………………..Class………………..Adm. No………..

Date done………..….Date marked……..……….Date revised………………

CHEMISTRY Form 2: Practice 1: Time 2 hours 80 marks

1. Study the information in the table below and answer the questions that follow (The letters do not represent the actual symbols of the elements)

 

Ionization Energy_kJ/Mole

Element

Electronic configuration

1st ionization energy

2nd ionization energy

A

2.2

900

1800

B

2.8.2

736

1450

C

2.8.8.2

590

1150

(i) What chemical family do the elements A, B and C belong? (1mk)

(ii)Write the formula and electronic structure of an ion of B(2mks)

Formula

Electronic structure

(iii)What type of bonding exist in(2mks)

  1. atoms of C
  1. chloride of B

(iv)What is ionization energy(1mk)

(v)Explain the following:

1.The 1st ionization energy is lower that the second ionization energy.(2mk)

 2.The 1st ionization energy of B is lower that of C.(2mk)

(vi)Write a chemical equation for the reaction of element B with:

1.Air

2.Chlorine gas

3.Steam(water vapour)

2.Study the information in the table below and answer the questions that follow ( the letters do not represent the actual symbol of the substances)

Substance

Melting Point (0C)

Boiling Point (0C)

Solubility in water

Density at room temperature g/cm3

H

J

K

L

-117

-78

-23

-219

78.5

-33

77

-183

Very soluble

Very soluble

Insoluble

Slightly soluble

0.8

0.77 x 10-3

1.6

1.33 x 10-3

(i)  Which substance would dissolve in water and could be separated from the solution by fractional distillation? Give a reason (2mk)

 

(ii)  Which substances is a liquid at room temperature and when mixed with water two layers would be formed? Explain (2mk)

(iii)  Which letter represents a substance that is gas at room temperature and which can be collected:

I. Over water? Explain (2mk)

II. By downward displacement of air? (Density of air is 1.29 x 10-3g/cm3 at room temperature).

Explain (2mk)

3. The grid below represents part of the periodic table. The letters do not represent the actual symbols.

  

A

B

  

X

G

P

Z

E

V

 

J

I

L

R

T

  

D

G

     

M

 

 

 

 

 

a) Select the most reactive

(i)non-metal. (1mk)

(ii)metal. (1mk)

 

b) Write the formula of the compound consisting of (10mk)

 1.D and Z only.

  2 . X and Z only

  3. Oxide of B

  4. Carbonate of J

5. sulphate of D

6. Nitrate of B

7. Chloride of X

8. Sodium compound of E

9. Aluminium compound of Z

10. Hydrogen compound of G

c) Select an element that can form an ion of charge (10mk)

(i) +1

(ii) -1

 (iii) +2

 (iv) +3

 (v) -3

d) Which element has the least ionization energy? Explain (2mks)

 

f) To which chemical family do the following elements belong? (3mk)

J

 

 E

 B

(g)When a piece of element G is placed in cold water, it sinks to the bottom and effervescence of a colourless gas that burns explosively is produced. Use a simple diagram to illustrate how this gas can be collected during this experiment. (3mks)

h) An element K has relative atomic mass of 40.2.It has two isotopes of masses 39 and 42. Calculate the relative abundance of each isotope. (3mks)

4. Balance the following chemical equation (6mk)

1.Ca (OH)2(aq) + Cl2(g) → CaCl2(aq) + CaOCl2(aq) + H2O(l)

 2.NaOH + Cl2(g) → NaClO3 (aq) + NaCl(aq) + 3H2O(l)

3.NaCl(s) + H2SO4(l) -> NaHSO4(aq) + HCl(g)

4.CaO(s) + H2O(l) -> Ca(OH)2(aq) + H2O(l)

5.Fe(s)  + HCl(aq) ->  FeCl3(aq) + H2 (g)

6.Zn(s) + HCl(aq) ->  ZnCl2(aq + H2 (g)

5.The diagram below shows a set up of apparatus for the school laboratory collection of dry chlorine gas.

Image From EcoleBooks.com

A) Name (2mk)

 (i) Substance Q

 (ii) Suitable drying agent L

b) State a missing condition for the reaction to take place faster. (1mk)

c) Moist red and blue litmus papers were dipped into the chlorine gas from the above set up .State and explain the observations made. (2mk)

d) Write the equation for the reaction taking place in the conical flask (1mk)

e) Name two other substances that can be used in place of MnO2 (2mk)

(f)State three uses of chlorine (3mk)

6. Study the set up below.

Image From EcoleBooks.com

a) Name salt K (1mk)

(b)Write the equation for the reaction for the formation of salt K (1mk)


(c)What property of salt A is exhibited as shown in the experiment.(1mk)

(d)What is the purpose of anhydrous calcium chloride? Explain (2mk)

(e)Name another metal that can be used to produce similar results (1mk)

7. In an experiment, dry hydrogen chloride gas was passed through heated zinc turnings as in the set up below. The gas produced was the passed through copper (II) oxide

Image From EcoleBooks.com

Write the equation for the reaction :

(i) for the preparation of hydrogen chloride gas. (1mk)

(ii)in tube S(1mk)  

 b)State and explain the observation made in tube V. (2mk)

  (c)How would the total mass of tube S and tube V and their contents compare before and after the experiment.

Tube S(2mk)

Tube V(2mk)

(d)Gas K was condensed to liquid K.

(i)Identify liquid K(1mk)

(ii)Describe a simple chemical test to identify Liquid K(3mk)

 

(iii)A small piece of sodium metal was placed into a beaker containing liquid K.

I. State three observations made( 3mk)

II.Write an equation for the reaction that take place(1mk)

III.What is the pH of the resulting solution. Explain(2mk)

8.Using dot(.) and cross(x) to represent electrons, show the bonding in.

(a)hydroxonium ion(H3O+)(2mk)

(b)Carbon(IV)oxide(CO2)(2mk)

(c)Carbon(II)oxide(CO)(2mk)

(d)Ammonia(NH3)(2mk)

(e)Ammonium ion(NH4+)(2mk)

(f)Magnesium chloride(MgCl2)(2mk)

(g)Ethane(C2H6)(2mk)

9.Study the set- up below and answer the questions that follow

Image From EcoleBooks.com

 

 

 

 

 

 

 

 

(a) Write an equation for the reaction, which take place in the combustion tube.

(b) What property of gas Z allows it to be collected as shown in the diagram

(c) State two uses of gas Z

 

 




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EcoleBooks | Chemistry Form 2 Notes :  SALTS

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2 Comments

  • EcoleBooks | Chemistry Form 2 Notes :  SALTS

    Stephen Ojwang, April 20, 2023 @ 8:57 am Reply

    This is exallent I like it , everyone should get this and Improve

  • EcoleBooks | Chemistry Form 2 Notes :  SALTS

    Stephen Ojwang, April 20, 2023 @ 8:56 am Reply

    Nice

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