Salt 2

1.SALT Ionic compound formed when the hydrogen ion, H+ from acid is replaced by a metal ion or ammonium ion, NH4+ 2.PREPARATION

3.QUALITATIVE ANALYSIS Qualitative analysis is a chemical technique used to determine what substances are present in a mixture but not their quantities. a) colour and solubility in water Salt / Cation / Metal Oxide

Colour in solid

Solubility in water

Colour in  Aqueous solution

K+, Na+, NH4+, Ca2+, Al3+, Zn2+, Pb2+

white

soluble

colourless

CuCO3

Green

Insoluble

-

Fe2+ ….FeSO4, Fe(NO3)2, FeCl2

Green

soluble

green

CuSO4, Cu(NO3)2, CuCl2

Blue

soluble

Blue

Brown

Soluble

Brown

White

Soluble in hot water

-

Black

Insoluble

-

Fe3+…..FeCl3,

Fe(NO3)3, Fe2(SO4)3 PbCl2 CuO

Yellow  hot  White  cold Brown  hot  Yellow  cold

PbO ZnO

Insoluble

-

Insoluble

-

b) Effect heat on salt

Salt

residue (cation)

+

Gas (anion)

(heat)

Salts

Colour of salt  before heating

CuCO3

Colour of residue Hot

cold

Green powder

Black

Black 

ZnCO3

White solid

Yellow

White

PbCO3

White solid

Brown

Yellow

Test on gases liberated The gas liberated turns lime water milky/chalky

Type of  Type of ion gas present(anion) produced CO3 2 except  CO2 Na2CO3 and K 2CO3 O2

NO3-

NO2

NO3- except  NaNO3 and KNO3

SO2

SO4 2-

NH3

NH4+

Anion Test 

Cation + add little NaOH

Blue

Fe2+

SO42-

NO3-

CO32-

HNO3

BaCl2

H2SO4

HNO3

AgNO3

HCl

FeSO4

White precipitate

Colour precipitate Green

Cl-

Brown Pb2+,Zn2+, Al3+

Fe3+

Cu2+

Mg2+ , Ca2+

 Add excess NaOH Coc. H2SO4

Soluble Pb2+

 Add KI solution

Insoluble

Zn2+, Al3+

Mg2+, Ca2+

 Add excess NH3

White precipitate formed

Brown ring formed

 Add SO42- ions

Efferves cence occur

DOUBLE DECOMPOSOSITION Yellow precipitate Pb2+

White precipitate soluble Zn2+

White precipitate insoluble Al3+

No change Mg2+

White precipitate

soluble salt + soluble salt solution

Ca2+

insoluble salt 

NH3

Example: preparing lead(II) chloride White precipitate

Colour precipitate

Fe2+

green

Cu2+

Blue

Fe3+

Brown

+ soluble salt solution

Pb(NO3)2

Al3+,Mg2+, Pb2+

Zn2+

 Add NH3 in excess Soluble Zn2+

NaCl

Insoluble Al3+ , Mg2+

Pb2+

PbCl2 NaNO3

 Add excess NaOH

 Add KI solution Pb(NO3)2 + 2NaCl

soluble Al3+

Insoluble Mg2+

Yellow precipitate Pb2+

Ionic eq: Pb2+ + Cl-

PbCl2 + 2NaNO3 PbCl2

SALT Ionic compound formed when the hydrogen ion, H+ from acid is replaced by a metal ion or ammonium ion, NH4+

Effect on heating salt  Metal oxide + C02 (residue) PbCO3

nitrate salt 

Carbonate salt 

PbO + CO2 Brown(hot), yellow(cold)

Ca2+

Metal oxide + N0 2 +O2 (residue)

2Pb(NO3)2

2PbO + 4NO2 + O2 Brown(hot), yellow(cold)

2Zn(NO3)2

2PbO + 4NO2 + O2 Brown(hot), yellow(cold)

2Cu(NO3)2

2CuO + 4NO2 + O2 Yellow(hot), white(cold)

2+

Mg

3+

Al ZnCO3

ZnO + CO2 Yellow(hot), white(cold)

2+

Zn

2+

Fe 2CuCO3 -reactive metal -metal oxide/metal carbonate

2CuO black 

+

CO2

Pb

2+ 2+

Cu