Chemistry Form 4 Chapter 8
Chapter 8: Salts
1. Salts A salt is an ionic compound. The anion part comes from the acid while the cation part comes from a base. Example: KCl, KOH(aq) + HCl(aq) KCl(aq) + H2O(l) A salt is a compound formed when the hydrogen ion. H+ from an acid is replaced by a metal ion or an ammonium ion, NH4+. Salts Nitrate salts Carbonate salts Chloride salts Soluble All nitrate salts Potassium carbonate, K2CO3 Ammonium carbonate, (NH4)2CO3 Sodium carbonate, Na2CO3 All chloride salts Except Sulphate salts All sulphate salts Except 2. Preparation and purification of soluble salts Lead (II) chloride, PbCl2 Silver chloride, AgCl Mercury Chloride, HgCl Lead (II) sulphate, PbSO4 Barium sulphate, BaSO4 Cacium sulphate, CaSO4 Persatuan Bahasa Cina Pb Ag Hg P A S All other carbonate salts Insoluble
i. ii. iii. iv.
The salts formed during preparation of soluble salts contain impurities. These salts need to be purified through a process known as recrystallisation. Physical characteristics of crystals: Crystals have fixed geometrical shapes such as a cuboid, rhombic or prism. Crystals of the same substance have same shapes but may be in different sizes. Crystals have flat surfaces, straight edges and sharp angles. Crystals have fixed angles between two neighboring surfaces.
Example 1: Preparation of Soluble Salts Na2SO4
© MHS 2009
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Example 2: Preparation of Soluble Salt MgSO4
3.
Preparation of insoluble salts An insoluble salts is prepared through precipitation reaction. Aqueous solutions containing the ions of the insoluble salt are mixed together to from the salt. The insoluble salt is formed as a precipitate and can be obtained by filtration. Example: BaCl2(aq) + Na2SO4(aq) BaSO4(s) + 2NaCl(aq) Insoluble salts can prepared by double decomposition reaction through precipitation.
© MHS 2009
2
4.
Procedure for the selection of the method preparing 1 specified salt.
5.
Qualitative Analysis of Salts Qualitative analysis is a
1. Salts A salt is an ionic compound. The anion part comes from the acid while the cation part comes from a base. Example: KCl, KOH(aq) + HCl(aq) KCl(aq) + H2O(l) A salt is a compound formed when the hydrogen ion. H+ from an acid is replaced by a metal ion or an ammonium ion, NH4+. Salts Nitrate salts Carbonate salts Chloride salts Soluble All nitrate salts Potassium carbonate, K2CO3 Ammonium carbonate, (NH4)2CO3 Sodium carbonate, Na2CO3 All chloride salts Except Sulphate salts All sulphate salts Except 2. Preparation and purification of soluble salts Lead (II) chloride, PbCl2 Silver chloride, AgCl Mercury Chloride, HgCl Lead (II) sulphate, PbSO4 Barium sulphate, BaSO4 Cacium sulphate, CaSO4 Persatuan Bahasa Cina Pb Ag Hg P A S All other carbonate salts Insoluble
i. ii. iii. iv.
The salts formed during preparation of soluble salts contain impurities. These salts need to be purified through a process known as recrystallisation. Physical characteristics of crystals: Crystals have fixed geometrical shapes such as a cuboid, rhombic or prism. Crystals of the same substance have same shapes but may be in different sizes. Crystals have flat surfaces, straight edges and sharp angles. Crystals have fixed angles between two neighboring surfaces.
Example 1: Preparation of Soluble Salts Na2SO4
© MHS 2009
1
Example 2: Preparation of Soluble Salt MgSO4
3.
Preparation of insoluble salts An insoluble salts is prepared through precipitation reaction. Aqueous solutions containing the ions of the insoluble salt are mixed together to from the salt. The insoluble salt is formed as a precipitate and can be obtained by filtration. Example: BaCl2(aq) + Na2SO4(aq) BaSO4(s) + 2NaCl(aq) Insoluble salts can prepared by double decomposition reaction through precipitation.
© MHS 2009
2
4.
Procedure for the selection of the method preparing 1 specified salt.
5.
Qualitative Analysis of Salts Qualitative analysis is a