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Transcript of CHAPTER 8 - WordPress.comwrite the step of preparation of the salts on the diagram] NaCl solution...
mohd faisol mansor/chemistry form 4/chapter 8
148
CHAPTER 8 SALTS
A salt is an ionic
substance produced
when the hydrogen
ion of the acid is
replaced by metal
ion or an ammonium
ion.
The salt consists of two
parts, cation from base
and anion from acid.
NaCl
NaOH
(Base)
HCl
(Acid)
mohd faisol mansor/chemistry form 4/chapter 8
149
Table of Salts
Complete the table below.
Metal ion Sulphate salt
(SO42-)
Chloride salt
(Cl-)
Nitrate salt
(NO3-)
Carbonate salt
(CO32-)
K+ K2SO4 KCl KNO3 K2CO3
Na+
Ca2+
Mg2+
Al3+
Zn2+
Fe2+
Sn2+
Pb2+
Cu2+
Ag+
NH4+
Ba2+
Based on the table above, mark the insoluble salt.
mohd faisol mansor/chemistry form 4/chapter 8
150
SOLUBLE & INSOLUBLE SALTS
SALT SOLUBLE INSOLUBLE
K+ , Na+ , NH4+ All soluble none
Nitrate salts
(NO3- )
All nitrate salts none
Chloride salts
(Cl-) All chloride salts
Lead (II) chloride,
PbCl2
Silver chloride, AgCl
Mercury chloride,
HgCl
Sulphate salts
(SO42-)
All sulphate salts
Lead (II) sulphate
Calcium sulphate
Barium sulphate
Carbonate
salts (CO32-)
Sodium carbonate,
Na2CO3
Potassium carbonate,
K2CO3
Ammonium carbonate,
(NH4)2CO3
All others carbonate
salts
Oxide salts
(O2-)
Sodium oxide, Na2O
Potassium oxide, K2O
Calcium oxide, CaO (slightly soluble)
All oxide salts
Hydroxide salts
(OH-)
Sodium hydroxide, NaOH
Potassium hydroxide, KOH
Calcium hydroxide,
Ca(OH)2
(slightly soluble)
All hydroxide salts
mohd faisol mansor/chemistry form 4/chapter 8
151
Preparation and Purification of Soluble Salts
Soluble salt can be prepared by the following ways:
1. Reaction between acid and alkali - preparation for
sodium, potassium and ammonium salts only.
Eg: HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)
Burette
HCl solution
NaOH solution
[write the step of preparation of the salts on the diagram]
NaCl solution
Evaporating dish
NaCl crystal salt
NaCl salt crystal
mohd faisol mansor/chemistry form 4/chapter 8
152
Preparation and Purification of Soluble Salts
Soluble salt can be prepared by the following ways:
1. Reaction between acid and metal oxide
Eg: HNO3(aq) + MgO(s) Mg(NO3)2 (aq) + H2O(l)
2. Reaction between acid and metal
Eg: H2SO4(aq) + Zn (s) ZnSO4(aq) + H2 (g)
3. Reaction between acid and metal carbonate
Eg: HCl(aq) + CaCO3(s) CaCl2(aq) + CO2(g) + H2O(l)
[write the step of preparation of the salts on the diagram]
heat heat
Copper(II) nitrate
Solution + excess
CuO
Copper(II) nitrate
solution
Evaporating Dish
Copper(II) nitrate solution
& crystal salt
Cu(NO3)2 crystal salt
mohd faisol mansor/chemistry form 4/chapter 8
153
Crystallization
is a process to crystallize
the soluble salts.
Recrystallization
process will carried out in
order to get pure and
more defined crystal
Physical characteristic of
crystals
Fixed geometrical shapes
such as a cuboids,
rhombic or prism
Flat surface, straight edges
and sharp angles.
Same shapes for same
substance but differ in
sizes
Fixes angle between two
neighbouring surfaces.
mohd faisol mansor/chemistry form 4/chapter 8
154
Preparation of insoluble salts
An insoluble salt is prepared through precipitation method.
Aqueous solution of two soluble salts are mixed to form
insoluble and soluble salt:
The reaction is called double decomposition.
Two solutions contain ions that make up the insoluble salts.
Eg: Preparation of lead(II) iodide salt by using lead(II)
nitrate solution and potassium iodide solution. [write the balance chemical equation]
Double Decomposition
[write the general equation of preparation insoluble salt]
mohd faisol mansor/chemistry form 4/chapter 8
155
Chemical and Ionic Equation
Chemical and ionic equation can be written for all reaction
That used to prepare salts.
Example: Formation of precipitate Barium Sulphate, BaSO4.
1. Chemical Equation:
BaCl2 (aq) + Na2SO4 (aq) BaSO4(s) + 2NaCl (aq)
2. Ionic Equation:
Ionic equation shows the ions take part in the reaction.
1. Change each of the following word equations to a balanced
chemical equation.
a) Sulphuric acid + zinc zinc sulphate + hydrogen gas.
b) Silver nitrate + potassium iodide silver iodide + potassium
nitrate
c) Nitric acid + chromium(III) hydroxide chromium(III) nitrate
+ water
Exercise
mohd faisol mansor/chemistry form 4/chapter 8
156
2. Complete the following equations.
a) HCl (aq) + NiO (s)
b) HNO3 (aq) + Ca(OH)2 (aq)
c) H2SO4 (aq) + MgCO3 (s)
3. Write an ionic equation for each reaction between the following
pairs of substances.
a) Sulphuric acid, H2SO4 and barium hydroxide, Ba(OH)2 solution
b) Ammonium chloride, NH4Cl solution and silver nitrate, AgNO3
solution.
c) Lead(II) nitrate, Pb(NO3)2 solution and copper(II) sulphate,
CuSO4 solution.
d) Iron(III) oxide, Fe2O3 and hydrochloric acid, HCl.
mohd faisol mansor/chemistry form 4/chapter 8
157
Constructing Ionic Equation using the Continuous Variation Method
Continuous variation method can be used to construct ionic
equation for the formation of insoluble salts.
Fixed volume of a reactant A is react with varying volumes
of a reactant B to determine the mole ratio of reactant A
that react completely with reactant B.
If x mol of reactant A with y mole of reactant B, than the
empirical formula for insoluble salt is A x B y.
Example:
2Fe3+ (aq) + 3CO32- (aq) Fe2(CO3)3 (s)
1 2 3 4 5 6 7 8
mohd faisol mansor/chemistry form 4/chapter 8
158
mohd faisol mansor/chemistry form 4/chapter 8
159
1. 6.0 cm3 of 0.2 mol dm-3 Xn+ solution reacts completely with 4.0
cm3 of 0.1 mol dm-3 Ym- solution to form a salt XmYn. Write the
ionic equation and hence determine the empirical formula of
the salt reaction.
2. 18.0 cm3 of 0.1 mol dm-3 solution of Px+ ions reacts completely
with 9.0 cm3 of 0.1 mol dm-3 solution of Qy- ions to form a salt
PyQx. Write the ionic equation and hence determine the
empirical formula of the salt in this reaction.
Example
mohd faisol mansor/chemistry form 4/chapter 8
160
Solving Problem Involving Calculation of Quantities of Reactants or
Product in Stoichiometric Reactions
Since the quantities of chemicals involved in a reaction are in term
of moles, the quantities of chemicals (volume, mass and number of
particles) must be converted to moles in calculation regarding
quantities of reactant and products.
1. Calculate the number of moles of aluminium sulphate
produced by the reaction of 0.2 mole of sulphuric acid with
excess aluminium oxide. [0.067 mole]
2. 2.0 g of sodium hydroxide reacts with excess sulphuric acid.
What is the mass of sodium sulphate produces
[RAM: H,1 ; O,16 ; Na,23 ; S,32] [ 3.55 g]
Exercise
mohd faisol mansor/chemistry form 4/chapter 8
161
3. What the volume of carbon dioxide gas evolved at s.t.p when
2.1 g of magnesium carbonate reacts with excess nitric acid.
[ RAM: C,12;O,16;Mg,24; s.t.p = 22.4 dm3] [ 560 cm3]
4. What is the mass of magnesium required to react with 20 cm3 of
2.0 mol dm3 hydrochloric acid to produce 120 cm3 of hydrogen
at temperature? [RAM: Mg,24 ; 1 mol = 24 dm3 at room temp.]
[ 0.12 g]
mohd faisol mansor/chemistry form 4/chapter 8
162
Qualitative Analysis of Salts
General procedure of qualitative analysis
Colour & Solubility of the Salt
GREEN PALE GREEN
Iron(II) Sulphate, FeSO4
Iron(II) Nitrate, Fe(NO3)2
Iron(II) Chloride, FeCl2
BROWN YELLOW/BROWN [depend on concentration]
Iron(III) Sulphate, Fe2(SO4)3
Iron(III) Nitrate, Fe(NO3)3
Iron(III) Chloride, FeCl3
REDDISH-BROWN INSOLUBLE
Iron(III) Oxide, Fe2O3
GREEN INSOLUBLE
Copper(II) Carbonate, CuCO3
BLUE BLUE
Copper(II) Sulphate, CuSO4
Copper(II) Nitrate, Cu(NO3)2
Copper(II) Chloride, CuCl2
BLACK INSOLUBLE
Copper(II) Oxide, CuO
Observations on the physical
properties of salts Action of heat on salts
Tests for cations and
anions
Confirmatory tests for
cations and anions
mohd faisol mansor/chemistry form 4/chapter 8
163
Colour & Solubility of the Salt
WHITE COLOURLESS
Potassium Oxide, K2O
Sodium Oxide, Na2O
Calcium Oxide, CaO
WHITE INSOLUBLE
Magnesium Oxide, MgO
Aluminium Oxide, Al2O3
INSOLUBLE
Zinc Oxide, ZnO
BROWN [hot]
INSOLUBLE
Lead(II) Oxide, PbO
WHITE [cold]
YELLOW [hot]
YELLOW [cold]
mohd faisol mansor/chemistry form 4/chapter 8
164
Gas test
HCl acid
Carbon dioxide Sulphur dioxide
HCl acid
Sodium Carbonate,
Na2CO3
Sodium Sulphite, Na2SO3
Oxygen gas hydrogen gas
Carbon dioxide gas sulphur dioxide gas
chlorine gas ammonia gas
White fumes
Glass rod dipped into
concentrated HCl acid
Ammonia gas, NH3 Chlorine gas, Cl2
Red litmus paper
Wooden splinter
Oxygen gas, O2 Hydrogen gas, H2
mohd faisol mansor/chemistry form 4/chapter 8
165
EFFECT OF HEAT ON SALTS
Sodium carbonate & potassium carbonate are very stable. They do
not decompose on heating.
Carbonate Salt Metal Oxide + Carbon dioxide
Salts Chemical Equation
1. Calcium carbonate
2. Magnesium carbonate
3. Aluminium carbonate
Salts Chemical Equation
1. Zinc carbonate
Carbonate salts
Heating
Heating
Carbonate salts [ white ]
residue [ white ]
Heating
Carbonate salts [ white ]
residue [ yellow – hot ] [ white – cold ]
mohd faisol mansor/chemistry form 4/chapter 8
166
Carbonate Salt Metal Oxide + Carbon dioxide
Salts Chemical Equation
1. Iron(III) carbonate
Salts Chemical Equation
1. Copper(II) carbonate
Salts Chemical Equation
1. Lead(II) carbonate
Heating
Carbonate salts [ brown ]
residue [ brown ]
Heating
Carbonate salts [ green ]
residue [ black ]
Heating
Carbonate salts [ white ]
residue [ brown – hot ]
[ yellow – cold ]
Heating
mohd faisol mansor/chemistry form 4/chapter 8
167
Carbonate Salt Metal + Carbon dioxide + Oxygen gas
Salts Chemical Equation
1. Mercury(II) carbonate
Salts Chemical Equation
1. Silver carbonate
Salts Chemical Equation
1. Aurum(II) carbonate
Heating
Carbonate salts [ white ]
residue [ grey ]
Heating
Carbonate salts [ white ]
residue [ shiny grey ]
Carbonate salts [ white ]
residue [ golden yellow ]
Heating
Heating
mohd faisol mansor/chemistry form 4/chapter 8
168
Nitrate Salt Metal Oxide + Oxygen gas + Nitrogen dioxide
Salts Chemical Equation
1. Calcium nitrate
2. Magnesium nitrate
3. Aluminium nitrate
Salts Chemical Equation
1. Zinc nitrate
nitrate salts
Heating
Heating
nitrate salts [ white ]
residue [ white ]
Heating
nitrate salts [ white ]
residue [ yellow – hot ] [ white – cold ]
mohd faisol mansor/chemistry form 4/chapter 8
169
Nitrate Salt Metal Oxide + Oxygen gas + Nitrogen dioxide
Salts Chemical Equation
1. Iron(III) nitrate
Salts Chemical Equation
1. Copper(II) nitrate
Salts Chemical Equation
1. Lead(II) nitrate
Heating
nitrate salts [ brown ]
residue [ brown ]
Heating
nitrate salts [ blue ]
residue [ black ]
nitrate salts [ white ]
residue [ brown – hot ]
[ yellow – cold ]
Heating
Heating
mohd faisol mansor/chemistry form 4/chapter 8
170
Nitrate Salt Metal + Nitrogen dioxide + Oxygen gas
Salts Chemical Equation
1. Mercury(II) nitrate
Salts Chemical Equation
1. Silver nitrate
Nitrate Salt Metal nitrite + Oxygen gas
Salts Chemical Equation
1. Potassium nitrate
2. Sodium nitrate
Heating
nitrate salts [ white ]
residue [ grey ]
Heating
nitrate salts [ white ]
residue [ shiny grey ]
Heating
Heating
Heating
nitrate salts [ white ]
residue [ white ]
mohd faisol mansor/chemistry form 4/chapter 8
171
TEST FOR ANIONS
Salt needed to be
dissolved into water
first to produce
aqueous salt
solution.
Unknown aqueous salt solution
[ state the procedure ] [ state the procedure ] [ state the procedure ] [ state the procedure ]
CONCLUSION CONCLUSION CONCLUSION CONCLUSION
OBSERVATION OBSERVATION OBSERVATION OBSERVATION [ label the diagram ] [ label the diagram ] [ label the diagram ] [ label the diagram ]
[ state the anion ] [ state the anion ] [ state the anion ] [ state the anion ]
Ionic Equation Ionic Equation Ionic Equation Ionic Equation
mohd faisol mansor/chemistry form 4/chapter 8
172
TEST FOR CATIONS
Salt needed to be
dissolved into water
(soluble salts) or in
dilute acid then
filtered (insoluble
salts) first to produce
aqueous salt solution.
Unknown aqueous salt solution
No precipitate White precipitate Coloured precipitate
Green
Brown
Blue
Add NaOH drop by drop
Add NaOH drop by drop until excess
Dissolve in excess NaOH Insoluble in excess NaOH
* All coloured ions insoluble in excess NaOH
mohd faisol mansor/chemistry form 4/chapter 8
173
TEST FOR CATIONS
Salt needed to be
dissolved into water
(soluble salts) or in
dilute acid then
filtered (insoluble
salts) first to produce
aqueous salt solution.
Unknown aqueous salt solution
No precipitate White precipitate Coloured precipitate
Green
Brown
Blue
Add NH3 drop by drop
Add NH3 drop by drop until excess
Dissolve in excess NH3 Insoluble in excess NH3
Dissolved in excess NH3
Dark blue solution
* Fe2+ & Fe3+ ions insoluble in excess NH3
mohd faisol mansor/chemistry form 4/chapter 8
174
Confirmatory Test for Cation
Cation Procedure Observation
Fe 2+
Fe 3+
Pb 2+
NH4 +
1. Identify the aqueous solutions based on the test and observation given.
Type Observation Answer
a. Potassium thiocyanate,
KSCN, solution is added. Blood red solution formed.
b. Potassium iodide, KI, solution
is added.
Yellow precipitate is
formed.
c. Ammonia solution, NH3, is
added until excess.
Blue precipitate dissolve to
form dark blue solution.
d. A little hydrochloric acid is
added.
Effervescene occur and
lime water turn into chalky.
e. A sulphuric acid, iron(II)
sulphate solution and
concentrated sulphuric acid
is added.
Brown ring formed.
f. Ammonia solution is added
until excess.
White precipitate
dissolved.
Exercise
ZnCl2 NaNO3 PbCl2 CuSO4 FeCl3 K2CO3