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CHAPTER 8SALT
Learning Outcomes
At the end of the lessons, students should be able to:
State examples of salts used in daily lifeExplain the meaning of salt Identify soluble and insoluble saltsDescribe the preparation of soluble salts.Describe the purification of soluble salts
by recrystallisation.List physical characteristics of crystals.
Uses of salts
Food preparation• NaCl-seasoning food• MSG- enhance food taste
Food preservation• NaCl- salted fish• NaNO2 -preserve prosessed
meat
Agriculture• Nitrate salts- fertilisers
Medical• CaCO3 –antacid that
reduce acidity in the stomach of gastric patients
• Salt is formed in neutralization.• Salt : ionic compound. – anion part – acid– cation part – base
• Definition of salts
KOH(aq) + HCl(aq) KCl(aq) + H2O
A salt is a compound formed when the hydrogen ion, H+ from an acid is replaced by metal ion or ammonium ion, NH4
+.
Anion from the acid
Cation from the base
Salt Solubility
• SOLUBILITY
An ability of a compound to dissolve in solvents
Depends on the cation and anion present
Types of salts Solubility in water
Sodium , Na Ammonium Potassium ,K
All are soluble
Nitrate All are soluble
Chloride All are soluble except PbCl2
AgCl and HgCl.
Sulphate All are soluble except PbSO4, CaSO4 and BaSO4
Carbonate salts All are insoluble except Na2CO3
(NH4)2CO3, ammonium carbonateK2CO3
NAK
PAH
PantaiCahaya Bulan
NAK
Type Of Salts
Soluble saltInsoluble salt
Salt that undissolve in water (at room temperature)
We must know whether the salt is
Soluble
or
Insoluble
Salt that dissolve in water
(at room temperature)
Before preparing salt:
Have different method to prepare salt
Soluble salts
•Sodium salts•Potassium salts•Ammonium salts
Preparation of soluble salts
Acid + alkali salt + waterExample: HCl + NaOH NaCl + H2O
Other saltsAcid + metal oxide salt + waterExample: CuO + H2SO4 MgSO4 + H2OAcid + metal salt +
hydrogen gasExample: Mg + H2SO4 MgSO4 + H2
Acid + metal carbonate salt + water + carbon dioxideExample: CaCO3 + 2HNO3 Ca(NO3)2 + H2O + CO2
HCl + NaOH NaCl
Titration method
Evaporation/Heating
Cooling/crystallization
Filtration
Dry
T-TitrationH- Heat
C- Cooling/Crystallisation
F- FiltrationD- Dry
Three Hot Cats
Frighten Dog.!!
How to remember ? ? ?
Zn + 2HCl ZnCl2 + H2
Add metallic oxide/metal/carbonate oxide
Heating
Filtration
Recrystallisation
A- Adding (Dissolve)
H- Heating
F- Filtration
R- Recrystallisation
Amazing Hat feels
rocks..!
How to remember ? ? ?
PURIFICATION OF SOLUBLE SALT
Impure Salt Dissolved in distilled water
Dilute solution + impurities
Heat and evoporate to get saturated solution + impurities
Saturated solution + impurities
Cool it. Crystallisation process begins
Pure crystals formed. Filter
crystal out.
PHYSICAL CARACTERISTICS OF CRYSTALS
NaCl
CuSO4
FeSO4
K2Cr2O7
KMnO4
Fixed geometrical shapes
Flat surface, straight edges and sharp angles.
Fixed angles between two adjacent surfaces.
Same substance have same shapes but different sizes