chapter 8 : salts
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Online learning to understand the concept and application of chemicals on the topic of salt. These slides were uploaded to help students understand the basic concepts of chemistry. Independent study in Freestyle.comTRANSCRIPT
CHAPTER 8: SALTS
W H O I S S A L T ?
W H O I S S A LT ?WHAT IS SALT ?
Ionic compound – formed when the hydrogen ion, H+ from an acid is replaced by a metal ion or an ammonium ion, NH4
+
REFER TEXT BOOK : PAGE 138
EXAMPLE :
Na+
NH4+
H ClMetal ions
Ammonium ion
Na+ Cl-
NH4+ Cl-
replace
replace
Ammonium chloride
Sodium chloride
SALTS CONSIST ANION PART COMES FROM THE ACID WHILE CATION PART COMES FROM BASES
Common cations
Common anions
(parent acids)
HCl
HNO3
H2CO3
H2SO4
Na+
K+
NH4+
Ca2+ Mg2+
Cu2+
Fe2+
Fe3+
Al3+ Zn2+
Pb2+
Metal ion
Sulphate salts
+ H2SO4
Chloride salts+ HCl
Carbonate salts
+ H2CO3
Nitrate salts
+ H2NO3
Na + Na2SO4 NaCl Na2CO3 NaNO3
Mg 2+ MgSO4 MgCl2 MgCO3 Mg(NO3)2
Cu 2+ CuSO4 CuCl2 CuCO3 Cu(NO3)2
Al 3+ Al2(SO4)3 AlCl3 Al2(CO3)3 Al(NO3)3
METAL ION DISPLACE H+ ION IN ACIDS
All nitrate salts ; soluble saltsBarium nitrate,
Ba(NO3)2
Calcium nitrate,
Ca(NO3)2
Aluminium nitrate,
Al(NO3)3
Silver nitrate, AgNO3
Lead(II) nitrate,
Pb(NO3)2
Potassium nitrate, KNO3
Sodium nitrate,NaNO3
Copper(II) nitrate,
Cu(NO3)2
Iron(III) nitrate,
Fe(NO3)3
SOLUBLE SALT
NO3-
ALL
All Na+, K+, NH4+ salts ; soluble salts
Potassium carbonate,
K2CO3
Sodium carbonate,
Na2CO3
Ammonium carbonate, (NH4)2CO3
Potassium sulphate,
K2SO4
Potassium chloride,
KCl
Potassium nitrate, KNO3
Sodium nitrate,NaNO3
Sodium chloride,
NaCl
Ammonium sulphate, (NH4)2SO4
SOLUBLE SALT
ALL
Na+, K+, NH4+
All carbonate salts ; insoluble saltsMagnesium carbonate
MgCO3
Calcium carbonate
CaCO3
Silver carbonate
Ag2CO3
Other names[hide]Silver(I)Carbonate
Copper(II) carbonate
CuCO3
Zinc carbonate
ZnCO3
Manganese(II) carbonateMnCO3
EXCEPTPotassium carbonate
K2CO3
SodiumCarbonate
Na2CO3
Ammonium carbonate
(NH4)2CO3
ALL
Na+, K+, NH4+
CO32-
INSOLUBLE SALT
EXCEPT
Mercury(II) Chloride
HgCl2
All SO42-, Cl- salts ; soluble salts
EXCEPT EXCEPTSilver(I) Chloride
AgCl
Lead(II) Chloride
PbCl2
SOLUBLE SALT
Cl-
ALLBarium
sulphateBaSO4
Lead(II) sulphate
PbSO4
Calcium(II) sulphate
CaSO4
SOLUBLE SALT
SO42-
ALLPb2
+
Ag+ Hg2
+
Pb2+
Ca 2+
Ba2+
EXCEPT
Copper(II) ChlorideCuCl2
Iron(II) ChlorideFeCl2
MagnesiumChlorideMgCl2
Copper(II) sulphateCuSO4
Aluminium(II) sulphate
Al2(SO4)3
ZincChlorideZnCl2
Potassium chloride,
KCl
Sodium chloride,
NaCl
INSOLUBLE SALT
SOLUBLE SALT
NO3-ALL ALL
CLASSIFICATION OF SALTS
PbSO4
CaSO4
BaSO4
PbCl2
AgCl
ALLCO3
2-
SO42-
Cl-
ALL
Na+, K+, NH4+
ALL
OTHER SOLUBLE SALTS
PREPARATION OF SALTS
SOLUBLE SALTS INSOLUBLE SALTS
ACID + ALKALI
NEUTRALISATION
[SPA]Sodium ,Na+ saltsPotassium, K+ salts
Ammonium, NH4+ salts
OTHER METHOD
ACID + METAL
ACID + METAL OXIDE
ACID + METAL CARBONATE
PRECIPITATION
INSOLUBLE SALT & SOLUBLE SALT
SOLUBLE SALT +SOLUBLE SALT
PREPARATION OF SOLUBLE SALTS
[ SODIUM SALTS / POTASSIUM SALTS / AMMONIUM SALTS ]
NEUTRALISATION REACTION
PREPARATION OF POTASSIUM CHLORIDE
EXAMPLE
K OH
ALKALI
H Cl
ACID
ClK H2O
SALTS
TITRATION METHOD – FIND OUT THE EXACTLY VOLUME OF ACID REQUIRED TO NEUTRALISE ALKALI.END POINT – POINT WHEN INDICATOR CHANGES COLOUR DURING TITRATION
NOTE : CONCENTRATION AND VOLUME OF ALKALI ARE KNOWN.
LET DO THIS: PREPARATION OF POTASSIUM CHLORIDE
APPARATUS : Pipette 25mL, Burette 50mL, Conical Flask 250 mLMATERIALS : Potassium hydroxide 1.0 M, Hydrochloric acid 1.0 M, Phenolphthalein
Use a pipette to transfer 25.0 cm3 of potassium hydroxide solution to a conical flask. Add 2 to 3 drops of phenolphthalein
Colourless KOH turn to pink.
Fill a burette with hydrochloric acid and record the initial burette reading.
Record the burette reading in 2d.p
Slowly adding the acid into the conical flask and swirls- until the indicator turns from pink to colourless. Record the volume of acid used. (V cm3)
Record the final burette reading in 2d.p
Pipette 25.0 cm3 of the same potassium hydroxide solution into a conical flask.Do not add any indicator.
From the burette, add exactly V cm3
of hydrochloric acid to the alkali and swirls and shake well.
PREPARATION OF POTASSIUM CHLORIDE
START OVER AGAIN BUT WITHOUT INDICATOR : To get the pure and neutral salt solution
RECRYSTALLISATION PROCESS[PURIFIED SOLUBLE SALTS]
HEATING/EVAPORATE
COOLING
FILTRATION
DRY
C R Y S TA L S A LT
Solution salt contains impurities continuous with recrystallisation process
PREPARATION OF SOLUBLE SALTS
[ OTHER SALTS EXCEPT Na+, K+, NH4+]
OTHER METHOD : DISSOLVE METAL IN ACID
Pour 50 cm3 of sulphuric acid into a beaker. Warm the acidUse a spatula to add copper(II) oxide powder bit by bit into the acid. Stir the mixture well. Continue adding copper(II) oxide until some of it no longer dissolves(excess unreacted metal
See the change of metal solid colour and dissolve
Solution salt contains impurities continuous with recrystallisation process
Glass rod
Acid
Metal/ metal oxide/ metal carbonate
Excess unreacted metal (residue)
Evaporating basin with salt solution (filtrate)
HEATING/EVAPORATE COOLING
Evaporating basin
Salt solution
RECRYSTALLISATION PROCESS [PURIFIED SOLUBLE SALTS]
FILTRATION
RECRYSTALLISATION PROCESS [PURIFIED SOLUBLE SALTS]
DRY C R Y S TA L S A LT
The crystals are filtered and rinsed with a little cold distilled water.
Rinse with
distilled water
Glass rod
Salt Cystals Filter Paper
These physical characteristics:• Regulars geometry shapes,
such as cubic or hexagonal.• Flat faces, straight edges and
sharp angles.• Same angle between adjacent
faces.
DISSOLVE SOLUTE IN ACID
HEATINGDISSOLVE METAL IN ACID
EXCESS METAL NOT DISSOLVE
COMPLETE REACT
NEUTRALISATION REACTION
1ST TITRATION WITH INDICATOR
FIND VOLUME OF ACID
2ND TITRATION NO INDICATOR
GET PURE SALT
PREPARATION OF SOLUBLE
SALTS
TRANSFER TO EVAPORATING
BASIN
HEATING/EVAPORATE
COOLING
FILTRATIONDRY
RECRYSTALISATION
C R Y S TA L S A LT
PREPARATION OF INSOLUBLE SALTS
[ ALL CARBONATE SALTS except Na+/K+/NH4+ ]
PbSO4 / CaSO4/ BaSO4/PbCl2/ AgCl ]
PRECIPITATION REACTION
PREPARATION OF LEAD(II) CHLORIDEEXAMPLE
Na Cl
SOLUBLE SALTS
Pb NO3
SOLUBLE SALTS
NO3Na
INSOLUBLESALTS
DOUBLE DECOMPOSITION METHOD – TWO AQUOUES SOLUTIONS/SOLUBLE SALTS WERE MIX TOGETHER INTERCHANGE TO PRODUCE TWO NEW COMPOUND WHICH IS INSOLUBLE SALT OR PRECIPITATE, AND AQUEOUS SOLUTION/SOLUBLE SALTS
Cl2Pb
the ions of the two aqueous solutions above interchange to produce two new compound which is insoluble salt or precipitate, and aqueous solution
[one of the solutions
contains the anions of the
insoluble salt]
two aquoues solutions/soluble salts were mix together
[one of the solutions
contains the cations of the
insoluble salt]
PR
EC
IPIT
AT
ION
RE
AC
TIO
N
Mixture solutions
Filter paper
Retort stand
Precipitate (residue)
Filter funnel
Aqueous Solution (filterate)
Glass rod
Filtration : Remove solution from precipitate
Glass rodDistilled
water
Precipitate (residue)
Rinse : remove other ions from precipitate
PR
EC
IPIT
AT
ION
RE
AC
TIO
N
FILTRATION RINSE
PR
EC
IPIT
AT
ION
RE
AC
TIO
N Filter paperPrecipitate/Soluble salts
Dry : Dried by pressing between two pieces of filter paper.
FLOW CHART : PREPARATION OF INSOLUBLE SALTS
MIX - STIRTWO SOLUBLE SALTS
FILTRATIONREMOVE FILTRATE
RINSEREMOVE OTHER IONS
DRYPRESS BETWEEN FILTER PAPER
PREPARATION OF SALTSREMEMBER : METAL ION DISPLACE
HYDROGEN ION IN ACID TO FORMED SALTS
HCl [H+/Cl-]Hydrochloric acid
HNO3 [H+/NO3-]
Nitric AcidH2SO4 [2H+/SO4
2-]Nitric Acid
H2CO3 [2H+/CO32-]
Nitric Acid
METAL / AMMONIUM ION
Na+
K+
NH4+
Ca2+
Mg2+ Cu2+
Fe2+Fe3+
Al3+
Zn2+
Pb2+
SU
MM
AR
IES
OF
RE
AC
TIO
N Method/Reaction Reason Type of Salts
(Metal) Neutralisation
(Titration method)Alkali + Acid Salts + Water
Most salts of sodium, potassium, and ammonium
ions are soluble.
Na+ K+
NH4+
Metal DisplacementMetal + Acid Salts + Hydrogen
More electropositive metal can be displaced hydrogen
ion from acid.
Ca2+
Mg2+
Al3+
Zn2+
Metal oxide + Acid Salts + Hydrogen Less electropositive metal not be displaced hydrogen
ion from acid.
Mostly Cu2+/Pb2+
/Ag+
Metal carbonate + Acid Salts + Water + Carbon dioxide
metal carbonate is a solid that cannot dissolves in
water, in reaction that solid must be added excessively
All above except
Na+/K+/NH4+
EXTRA INFO : REMEMBER
Reactive metal is magnesium, aluminium, and zinc. Unreactive metal is iron, lead, silver
Metal that is less reactive from hydrogen such as copper, lead and silver did not react with dilute acid.
Soluble salts of sodium, potassium and ammonium can be prepared by the reaction between an acid and alkali.
Metal, metal oxide and metal carbonate is a solid that cannot dissolves in water, hence during reaction that solid must be added excessively to make sure all hydrogen ions in acid is completely reacted. Excess solid can be expelling through filtration.
Unreactive metal such as lead (Pb), copper (Cu), and silver (Ag) cannot react with dilute acid. So to prepare salt contains lead ions (Pb2+), copper ions (Cu2+) or silver ions (Ag+), we must use either oxide powder or carbonate powder only.
Impure soluble salt can be purified through crystallization process
EXTRA INFO : REMEMBER
