P&P notes Chapter 8 【Salts】

CHAPTER 8 : SALTS
7.1 SALTS
1. What is salt ?
It’s a ___________ compound which formed when the _______________ ________ from acid is replaced by a metal ion or ammonium ion.

Example: NaOH + HCl --> NaCl + H2O

2. Some of the salts are soluble and some are insoluble.
Salts Soluble √ Insoluble X
Sodium salts
Na+ • All soluble ------
Pottasium salts
K+ • All soluble ------
Ammonium salts
NH4+ • All soluble ------
Nitrate salts
NO3- • All soluble ------
Carbonate salts
CO32- • Sodium carbonate, Na2CO3
• Potassium carbonate,
K2CO3
• Ammonium carbonate,
(NH4)2CO3
• All other carbonate salts insoluble
Chloride salts
Cl- • All chloride salts • Lead(II) chloride, PbCl2
• Silver chloride, AgCl
Sulphates salts
SO42- • All chloride salts • Lead (II) sulphate, PbSO4
• Calcium sulphate, CaSO4
• Barium Sulphate, BaSO4
Ions Soluble √ Insoluble X
Oxide
O2- • Only Sodium oxide, Pottasium oxide,
Ammonium oxide soluble • All others insoluble
Hydroxide
OH- • Only Sodium hydroxide, Pottasium hydroxide,
Ammonium hydroxide soluble • All others insoluble

* try to determine the salts whether its soluble @ insoluble

1. Sodium hydroxide
2. Magnesium hydroxide
3. Barium nitrate
4. Copper (II) chloride
5. Ammonium sulphate

7. Lead (II) nitrate
8. Zinc sulphate
9. Copper (II) sulphate
10.Pottasium carbonate
11.Aluminium oxide
6. Lead (II) chloride 12.Silver sulphate


Group 1: Soluble salts of Na+ , K+ & NH4+
Group 2: Soluble salts which not Na+ , K+ & NH4+
Group 3: Insoluble salts

7.2 THE PREPARATION OF SOLUBLE SALTS OF GROUP 1
acid (aq) + alkali (aq)  (neutralisation)

-recrystallisation can be done by repeating:



- recrystallisation repeated to get the ___________ salt.


7.3 THE PREPARATION OF SOLUBLE SALTS OF GROUP 2
1. acid (aq) + base (s) 
2. acid (aq) + metal (s)  ( x Cu & Ag)
3. acid (aq) + metal oxide (s) 
4. acid (aq) + metal carbonate (s) 

7.4 THE PREPARATION OF INSOLUBLE SALTS OF GROUP 3
1. soluble salt solution ( cation) + soluble salt solution ( anion) 

7.5 NUMERICAL PROBLEM SOLVING
Step 1 : Write balance equation
Step 2 : Find No. of mole of substance which given info
Step 3 : Compare No. of mole
Step 4 : Get answer

* Exercises



7.6 QUALITATIVE ANALYSIS OF SALTS
Qualitative analysis – a chemical technique to determine what substances are present in a mixture but not their quantities.
Aim: To find out types of cation & anion which present.

Observation on the physical properties:
1. colour
2. solubility in water
3. test of produced gases
4. action of heat on salts
5. test for anions
6. test for cations


1.Colour
Cations in aq Colour Anion in aq Colour Solid salt Colour
Fe2+ Pale green NO3- colourless Fe2+ salts Green
Fe3+ Brown SO42- colourless Fe3+ salts Brown
Cu2+ Blue Cl- colourless Iron (III) Oxide Reddish Brown
Other colourless CO32- colourless Zinc Oxide Yellow –hot
White - cold
Lead (II) Oxide Brown – hot
Yellow - cold
Copper (II) Oxide Black
Cu2+ salts Blue
Other salts White

2. Solubility in Water
** refer to the table 7.1 (2)




3. Test of Produced Gases
Method of Tests Observation Acidic / Alkaline Gases
• tested by glowing splinter • • neutral O2
• tested by wooden splinter • • Little acidic H2
• gas bubbled through lime water • • Little acidic CO2
• Moist red litmus paper
• Tested by a drop of concentrated HCl • Red litmus paper turns blue
• Dense white fume formed • alkaline NH3
• Moist red / blue litmus paper • blue litmus paper turns red• • Little acidic Cl2
• Moist blue litmus paper
• Tested by a drop of concentrated NH3 • blue litmus paper turns red
• produce • acidic HCl
• Moist blue litmus paper
• Tested by a drop of acidified potassium manganate (VII) solution
• Tested by a drop of acidified potassium dichromate (VI) solution • blue litmus paper turns red
• decolourises the purple colour

• turns colour from orange to green • acidic SO2
• Moist blue litmus paper • Brown gas • acidic NO2


4. Action of Heat on Salts
Carbonate Salts Action of Heat Nitrate Salts Action of Heat
K2CO3
Na2CO3
Not decomposed by heat KNO3 NaNO3 2KNO3  2KNO2 + O2
CaCO3
MgCO3
Al2(CO3)3
ZnCO3
FeCO3
PbCO3
CuCO3 CaCO3  CaO + CO2 Ca(NO3)2
Mg(NO3)2
Al(NO3)3
Zn(NO3)2
Fe(NO3)2
Pb(NO3)2
Cu(NO3)2
Ag2CO3
AgNO3
(NH4)2CO3 NH4NO3

- most the sulphate salts are not decomposes by heat, only a few sulphate salts decompose when heated strongly
- all the chloride salts are not decomposes by heat, except ammonium chloride
NH4Cl (s)  NH3 (g) + HCl (g)



5. Test of Anions ( -ve)

Anions Method
CO32- + 2 cm3 dilute HCl
Tested by lime water
-
SO42- + >>> dilute HCl
+ BaCl2 & shaked
-
Cl- + >>> dilute HNO3
+ AgNO3 & shaken well
-
+ NH3 & shaken well
-
NO3- + 2 cm3 dilute H2SO4
+ 2 cm3 FeSO4 & shaken well
+ Few drops of concentrated sulphuric acid dropped slowly along the side of a slanting test tube without shaking
-



7. Test of Cations
* refer to pg. 232 and complete the chart below
Add few drops of NaOH