Chemistry Salt 2
Transcript of Chemistry Salt 2
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CHAPTER 8: SALTS
1. Classification andpreparation of salt
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Neutralisation using titration
Titration method
Evaporation/Heating
Cooling/crystallization
Filtration
Dry
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Salt Preparation
Salt type
(Na+, K+, NH4+)
Other than
(Na+, K+, NH4+)
Soluble salts Insoluble salts
Neutralisation Acid + Metal oxide
Acid + metallic carbonate
Acid + Metal
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Preparation of soluble salts other
than (Na+, K+, NH4+)
1. Acid + metal oxide Salt + water
Eg: HCl + MgO MgCl2 + H2O
2. Acid + metal Salt + hydrogen gas
Eg: 2HCl + Zn ZnCl2 + H2
3. Acid + metal carbonate Salt + water + carbon
dioxide
Eg: HCl + CuCO3 CuCl2 + H2O + CO2
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Metal/ metal oxide/
metal carbonate
Glass rod
Acid
Pour 50 cm3of sulphuric acid
into a beaker. Warm the acid.
Use 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 unreactedmetal).
Step 1 -
Heating
See the change of metal solid
colour and dissolve
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Step 2 -
Filtration
Excess
unreacted
metal (residue)
Evaporating basinwith salt solution
(filtrate)
Solution salt contains
impurities.
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Step 3 Heating/Evaporation
Evaporatingbasin
Saltsolution
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Step 4 -
Cooling
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Step 5 -
Filtration
Step 6
Drying
Rinse
with
distilled
water
Glass
rod
Salt Cystals
The crystals are
filtered and rinsedwith a little cold
distilled water.
Filter
Paper
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Recrystallisation
Purpose: To purify impure salts because thesalts contain impurities
Steps:
1. Addingdistilledwater to
impure salt
2. Repeatheating/evaporation,
cooling, filtrationand drying process
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Regular geometricshapes such as cubicor hexagonal
Straight and sharpedges
Flat and smoothsurfaces
Surfaces that makedefinite angles withone another
Hard but brittle
Salt crystal characteristic
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Fastcrystallisation small crystals
Slow
crystallisation large crystals
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Now lets watch a
video aboutRecrystallisation
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Preparation of insoluble salts
Precipitation method
1. Mix two soluble salts aqueous solutions together
and react to form an insoluble salt and solublesalt.
Example:
Barium nitrate + sodium sulphate
Barium sulphate + sodium nitrate
2. This reaction is called double decomposition.
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Two aqueous solutions/soluble salts were
mixed together
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Mixture solutions
Filter paper
Retort
stand
Precipitate
(residue)
Filter
funnel
Aqueous
Solution
(filterate)
Glass
rod
Glass
rodDistilled
water
Precipitate
(residue)
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Filter paperPrecipitate
/Soluble
salts
Dried by pressing between two
pieces of filter paper.
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Do Activity 8.5
I l bl S l l i Ch i l E i I i
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Insoluble
Salt
Salt solution Chemical Equation Ionic
EquationCation Anion
Zinccarbonate,
ZnCO3
Zn(NO3 )2 Na2CO3 Zn(NO3 )2 + Na2CO3 ZnCO3 + 2NaNO3
Zn2+ + CO32- ZnCO3
Barium
sulphate,
BaSO4
Ba(NO3)2 K2SO4 Ba(NO3)2+K2SO4 BaSO4+ 2KNO3
Ba2+ + SO42-
BaSO4
Lead (II)
sulphate,PbSO4
Pb(NO3 )2 Na2SO4 Pb(NO3 )2 + Na2SO4
PbSO4 + 2NaNO3
Pb2+ + SO42-
PbSO4
Lead (II)
iodide,
PbI2
Pb(NO3 )2 KI Pb(NO3 )2 + 2KI
PbI2 + 2KNO3
Pb2+ + 2I-
PbI2
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Conclusion
Preparation ofsalts
Soluble Salts
Na+, K+, NH4+ -
Neutralisation
Other than Na+,K+, NH4
+
reaction withmetal, metal
oxide or metalcarbonate
Insoluble Salts Precipitationmethod