Main Classes of Inorganic Compounds
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Inorganic compounds
-
Inorganic compounds usually dissolve in water;
-
Inorganic compounds generally do not dissolve in organic solvents;
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Inorganic compounds usually have high melting points and boiling points.
They usually do not decompose on heating;
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Inorganic compounds usually non inflammable; they do not burn easily;
-
Most of inorganic compounds are ionic, so they are electrolytes.
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Cont..
Inorganic compounds include compounds that are made up of two or more elements.
Inorganic compounds are most often classified in terms of the elements or groups of
elements that they contain.
Compounds
Oxides
Bases
Acids
Salts
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Acid
 Acid solutions contain more H+ ions than OH- ions.
 Acids that dissociate (ionize) to a large extent are strong electrolytes
and Strong Acids. Acids that dissociate only to a small extent are
weak Acids and weak electrolytes
Physical Properties of ACIDS
 Acids taste sour (e.g. vinegar, lemon juice).
 Acids are harmful to living cells.
 Aqueous solutions of all acids contain hydrogen ions.
 Acid turns blue litmus red.
 Strong acids are corrosive.
 They conduct electricity in aqueous solutions.
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Chemical Properties of Acids
 With metals
• Metals above copper in the reactivity series will react with acids, giving off
hydrogen gas, forming a salt.
Mg(s) + H2SO4(aq)  MgSO4(aq) + H2(g)
 With bases (metal oxides and hydroxides)
• The base dissolves in the acid and neutralizes it. A salt is formed.
H2SO4(aq) + CuO(s)  CuSO4(aq) + H2O(l)
 With metal carbonates
• With metal carbonates, effervescence occurs, salt, water and carbon dioxide
gas is produced.
2HCl(aq) + CaCO3(s)  CaCl2(s) + H2O(l) + CO2(g)
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Basicity of Acid
• It is the number of ionizable H+ ions present in an acid e.g.
• HCl is monobasic, it ionizes to produce one H+ ion
HCl ============== H+ + Cl• H2SO4 is Dibasic, It ionizes to produce two H+ ions.
H2SO4 =============== 2H+ + SO42• H3PO4 is Tribasic, it ionizes to produce three H+ ions.
H3PO4 ============== 3H+ + PO43-
Acidity of a Base
• It is the ionizable OH- ions present in an alkali. e.g.
NaOH is monoacidic
NaOH ========== Na+ + OH• Ca(OH)2 is diacidic
Ca(OH)2 ============== Ca2+ + 2OH6
Common Strong Acids & their Anions
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Common Weak Acids & their Anions
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Bases
 Bases belong to the class of inorganic compounds that include most
oxides and hydroxides of metals.
 They are of great importance in chemical industries and in our daily
lives, directly or indirectly.
For example, sodium hydroxide, NaOH is used in the production of
soap, paper, textile etc.
Potassium hydroxide, KOH is used to produce soft soap, fertilizers etc.
Calcium hydroxide,
Ca(OH)2 is used to manufacture mortar and bleaching powder, to
remove soil acidity etc.
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Physical Properties of Acids & Bases
•
Bases like NaOH, KOH, and Ba(OH)2 are readily soluble in water,
while others such as Mg(OH)2 are slightly soluble. Bases that are
soluble in water are also called alkalis.
•
Bases are slippery to the touch and have a bitter taste.
•
Soluble bases change the color of indicators.
•
Soluble bases release hydroxide ion in aqueous solution.
•
Aqueous solutions of bases conduct electricity.
•
Bases neutralize acids or acidic oxides to form salt and water.
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Chemical Properties of Bases
• Alkali's are used to produce the insoluble hydroxide precipitates of many
metal ions from their soluble salt solutions.
2NaOH(aq) + CuSO4(aq) ==> Na2SO4(aq) + Cu(OH)2(s)
ionically: Cu2+(aq) + 2OH-(aq) ==> Cu(OH)2(s)
• Alkali's are used to produce the insoluble hydroxide precipitates of
many metal ions from their soluble salt solutions.
2NaOH(aq) + CuSO4(aq) ==> Na2SO4(aq) + Cu(OH)2(s)
– ionically: Cu2+(aq) + 2OH-(aq) ==> Cu(OH)2(s)
• This reaction can be used as a simple test to help identify certain metal
ions.
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OXIDES
Oxygen forms compounds with all elements except He, Ne, Ar, and
Kr. It reacts directly with all elements except the halogens, a few
noble metals e.g. Ag and Au and the noble gases.
The alkali metals and alkaline earth metals form three different types
of binary oxygen compounds:
(1) oxides, containing oxide ions, O2-
(2) peroxides, containing peroxide ions, O22−, which contain oxygenoxygen covalent single bonds, and
(3) superoxide's, containing superoxide ions, O2− , which also have
oxygen-oxygen covalent bonds but with one fewer negative
charge than peroxide ions.
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Cont..
Based on their acid-base characteristics oxides are classified as
acidic or basic, neutral and amphoteric.
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Acidic Oxides
Acidic oxides are the oxides formed by the chemical combination of
oxygen with nonmetals. Thus, acidic oxides are non-metal oxides.
These oxides are also called acid
anhydrides, since they form acidic solutions when reacted or
dissolved in water. Acid
anhydride means acid without water.
Chemical Properties of Acidic Oxides
Acidic oxides undergo the following reactions:
Acidic oxides (acid anhydrides) dissolve in water to form acidic solution (acid).
Acidic oxides react with basic or metallic oxides to form salt.
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Basic Oxides
Oxides that are composed of metals and oxygen are basic oxides.
But, all metal oxides are not necessarily basic oxides.
The oxides of active metals, group IA and heavier members of group
IIA, dissolve in water and readily form bases.
The term base is used to describe both soluble and insoluble basic
oxides.
Some examples of basic oxides are Li2O, Na2O, K2O, MgO, CaO,
BaO, and CuO.
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Chemical Properties of Basic Oxides
Basic oxides dissolve in water to form alkaline solutions. As they
dissolve, they
react with water to form the corresponding metal hydroxides.
CaO + 2HCl == CaCl2 +H2O
CuO + H2SO4 == CuSO4 +H2O
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Amphoteric Oxides
There are oxides which exhibit both acidic and basic properties.
These are known as amphoteric oxides.
examples of amphoteric oxides are ZnO, PbO, PbO2, SnO, and SnO2.
What is the common characteristic of acidic, basic and amphoteric
oxides?
Acidic oxides form salts when reacted with basic oxides and bases.
Basic oxides also produce salts in their reactions with acidic oxides
and acids. Amphoteric oxides form salts when they react with acids
and bases. Thus, acidic oxides, basic oxides and amphoteric oxides
are salt-forming oxides.
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Neutral Oxides
Neutral oxides react neither with acids nor with bases to form salt
and water.
Hence, neutral oxides do not show basic and acidic properties.
Examples of neutral oxides are:
• water, H2O,
• carbon monoxide, CO,
• dinitrogen monoxide, N2O, and
• nitrogen monoxide, NO. N
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PERIODIC TRENDS IN OXIDES
In any given period, the bonding in oxides progresses from ionic to covalent, and
their acid-base character goes from strongly basic through weakly basic,
amphoteric, weakly acidic, and finally strongly acidic.
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SALTS
Salts are ionic compounds which contain positively charged cations
and negatively charged anions.
During salt formation cation is coming from base and anion is coming
from acid.
Example: In Sodium chloride (NaCl) formation cation sodium is
coming from sodium hydroxide and anion chlorine is coming from
hydrochloric acid.
Note: Ammonia is an unusual base - it does not contain a metal. It
forms ammonium salts, containing the ammonium ion, NH4+.
e.g.
NH3(aq) + HNO3(aq)  NH4NO3(aq)
(ammonium nitrate)
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Classification of salts
• Normal salts: These salts are formed by the complete replacement of
hydrogen in acids by other metal cations from the bases. NaCl is normal
salt formed by the reaction of HCl with NaOH.
HCl + NaOH → NaCl + H2O
Acidic salts: Salts which are formed by the partial replacement of hydrogen
atoms of acids are called acidic salts. Example: NaHSO4 is formed when
partial replacement of hydrogen atoms by the sodium atoms of base.
H2SO4 + NaOH → NaHSO4 + H2O
Basic salts: Salts which are formed by the partial replacement of hydroxyl group are
called basic salts. Example: Ca(OH)Cl is formed by the partial replacement of hydroxide
group from Ca(OH)2 by chloride ions of acid.
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Cont.…
Double salts: Salts that are formed by mixing of two simple salts
which are obtained crystallization.
Example: Potash alum (K2SO4 Al2(SO4)3.24H2O), Dolomite –
(CaCO3.MgCO3).
Complex salts: The salts which contains different types of metal
atoms which on hydrolysis produces complex ions along with simple
ions are called complex salts.
[Ag(NH3)2]Cl ⇄ [Ag ( NH3 )2 ] + + Cl
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Cont..
In general these salts formed when the reacted acid is not sufficient for the
neutralization of base. Table below giving neutral, acidic and basic salts.
Table 2.1 classification of salts with examples.
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Methods of making Soluble Salts
Method 1 (Acid + Metal)
• Not suitable for making salts of metals above magnesium, or
below iron/tin in reactivity.
• e.g.
Zn + 2HCl ------------- ZnCl2 + H2
Fe + H2SO4 ---------------- FeSO4 + H2
Method 2 (Acid + Base)
• Useful for making salts of less reactive metals, e.g. lead,
copper.
• e.g.
CuO + H2SO4 --------- CuSO4 + H2O
MgO + 2HCl ------------- MgCl2 + H2O
• Add excess base to acid.
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• Method 3 (Acid + Carbonate)
• Useful particularly for making salts of more reactive metals, e.g.
calcium, sodium.
• e.g.
• CaCO3 + 2HCl ------ CaCl2 + H2O + CO2.
• Na2CO3 + H2SO4 ---- Na2SO4 + H2O + CO2.
• Method 4 (Acid + Alkali)
• This is useful for making salts of reactive metals, and ammonium
salts. It is different from methods 1-3, as both reactants are in
solution. This means neutralisation must be achieved, by adding
exactly the right amount of acid to neutralise the alkali. This can be
worked out by titration
• e.g.
• NaOH + HCl ----------- NaCl
+ H2O
• 2NH4OH + H2SO4 -----(NH4)2SO4 + 2H2O
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Making Insoluble Salts
• This involves mixing solutions of two soluble salts that between
them contain the ions that make up the insoluble salt. It is made
by two methods.
– PRECIPITATION
• BaCl2(aq) + MgSO4(aq)
 BaSO4(s) + MgCl2(aq)
– DIRECT COMBINATION
• Fe + S ---heat---- FeS
PRECIPITATION REACTION
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Types of Salts
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Double salts: Salts that are formed by mixing of two simple salts
which are obtained crystallisation. Example:
Potash alum - K2SO4 Al2 (SO4) .24H2O
Dolomite - CaCO3.MgCO3
Complex salts: The salts which contains different types of metal
atoms
which on hydrolysis produces complex ions along with simple ions
are called complex salts. Example:
[Ag(NH3)2]Cl ⇄ [Ag ( NH3 )2 ]+ + Cl
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HYDRATED & ANHYDROUS SALTS
• Hydrated Salt: Salt that contains Water of
Crystallization is called Hydrated Salt e.g. CuSO4.5H2O,
Na2CO3.10H2O.
• Anhydrous Salt: Salt with out Water of Crystallization
is called Anhydrous Salt. e.g. CuSO4, Na2CO3
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Salts in our daily life
The salts are essential for the normal functioning of a human body like
sodium, potassium, magnesium ions, etc.
1) Baking soda: NaHCO3 – sodium hydrogen carbonate. It is used in
the baking industry, preparation of soda acid & foam type fire
extinguishers
2) Washing soda: Na2CO3•10H2O – sodium carbonate decahydrate
or washing soda.
Na2CO3.10H2O + Exposure to open dry air → Na2CO3.H2O + 9H2O
Na2CO3.H2O + Heating → Na2CO3
Sodium carbonate is used to manufacture of glass, cleansing agents, soap, glass and
paper.
3) Bleaching powder (CaOCl2): used to disinfect drinking water
Coloured matter + Bleaching powder → Colourless product
CaOCl2 + H2S → CaCl2 + H2O + S
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USES OF SALTS
S.No
.
SALT
USE
1
Ammonium Chloride
In torch batteries
2
Ammonium Nitrate
In fertilizers
3
Calcium Chloride
As drying agent
4
Iron Sulphate
In Iron tablets
5
Magnesium Sulphate
In medicine
6
Potassium Nitrate
In gunpowder etc.
7
Silver Bromide
In photography
8
Sodium Chloride
Making NaOH
9
Sodium Stearate
In making soap.
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INDICATORS.
•Indicators are the substances that have different colors in acidic
and in alkaline solution.
No.
Color in strong pH at which
acidic solution color change
Color in strong
alkaline
solution
1 Methylorange
Red
4
Yellow
2 Bromothymol
Yellow
7
Blue
9
Red
4
Green
3
4
Indicator
blue
Phenolphthalei Colorless
n
Red
Screened
methylorange
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pH Graph
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Exercises
1. State the different properties of acids, bases and salts
2. Which acid is found in oranges and lemons?
3. Why nitric acid is strong acid while acetic acid is a weak acid ?
4. You have been provided with three test tubes. One of them
contains distilled water and the other two contain an acidic solution
and a basic solution, respectively. If you are given only red litmus
paper, how will you identify the contents of each test tube?
5. Why should curd and sour substances not be kept in brass and
copper vessels ?
6. Which gas is usually liberated when an acid reacts with a metal?
Illustrate with an example. How will you test for the presence of this
gas?
7. Metal compound A reacts with dilute hydrochloric acid to produce
effervescence. The gas evolved extinguishes a burning candle. Write
a balanced chemical equation for the reaction if one of the
compounds formed is calcium chloride.
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8. Why does dry HCl gas not change the colour of the dry litmus paper?
9. Can an oxide be neither acidic nor basic?
10. BaO2 is which of the following: hydroxide, peroxide, or superoxide?
11. Classify the following oxides; CaO, NO, N2O, Li2O, Cl2O7, CO,
Mn2O4, BaO2, SrO
12. Why is it not possible to obtain oxygen directly from water?
13. What is the correct name for a) FeO; b) Al(NO3)3; c) BeC2O4;
d) NH4MnO4; e) CoS2O3
14. What is H3P?
15. While diluting an acid, why is it recommended that the acid should be
added to water and not water to the acid?
16. You have two solutions, A and B. The pH of solution A is 6 and pH of
solution B is 8. Which solution has more hydrogen ion concentration?
Which of this is acidic and which one is basic?
17. A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(b) Why does this milk take a long time to set as curd?
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