Acids Bases and Salts
·
Natural indicator
of acids and bases – Litmus, Turmeric
·
Synthetic
indicator of acids and bases – Methyl Orange, Phenolphthalein
·
Olfactory
indicators of acids and bases - Odor of these substance changes in acids and
bases.
pH scale for Acid Neutral and Alkaline (or Base) & Acid Base strength indication by H and OH ion concentration |
What is Acid?
Acids are the chemicals which
can donate a proton or accept an electron
pair in chemical reactions having pH less than 7 and changes color of blue
Litmus to red.
Example- HCl, H2SO4
What is Base?
Bases are the chemicals which
can accept a proton or donate an electron
pair in chemical reactions having pH more than 7 and changes color of red
Litmus to blue.
Bases which dissolve in water
are called as Alkali
Example- NaOH
What is Salt?
Salt is a mineral or any neutral compound containing cations (+ve ions) attached with anions (-ve ions).
Example- NaCl
Acids and Bases Reaction with Metals:-
Metal react with acid to form salt.
Acid + Metal ------> Salt + Hydrogen Gas
Similarly,
Metal react with base to form salt.
Base + Metal -------> Salt + Hydrogen Gas
Reaction of Metal Carbonates and Metal Hydrogen-Carbonates with Acids:-
Metal carbonates and metal
hydrogen carbonates react with acids to form salt, water and carbon dioxide.
Metal Carbonate + Acid ----> Salt + Water + Carbon Dioxide
Example- Na2CO3
+ 2HCl ---> 2NaCl + H2O
+ CO2
Similarly,
Metal Hydrogen Carbonate +
Acid --> Salt + Water + Carbon
Dioxide
Example- NaHCO3 + HCl
---> NaCl + H2O
+ CO2
Reaction of Acids with Bases:-
Reaction of acids with bases
to form salt and water is called neutralization reaction.
Acid + Base ----> Salt + Water
Reaction of Acids with Metallic Oxides:-
Acids react with Metallic
Oxides to form salt and water.
Acid + Metallic Oxide ----> Salt + Water
Reaction of Bases with Non-Metallic Oxides:-
Non-Metallic Oxides are
acidic in nature so these react with bases to form salt and water.
Base + Non-Metallic Oxide ----> Salt + Water
Acids or Bases in Water:-
When acids dissolve in water
they produce Hydrogen Ion H+(Aq) or Hydronium Ion (H3O+)
HCl + H2O ----> H3O+ + Cl-
H+ + H2O
---> H3O+
When bases dissolve in water
they produce Hydroxide Ions (OH-)
NaOH + H2O -------> Na+(Aq) + OH-(Aq)
Reactions of Acids or Bases
with Water are highly exothermic. Process of mixing Acid or Base with water
decrease concentration of ions per unit volume, this process is known as dilution.
Strength of Acids or Bases:-
Strength of acids depends on
number of hydrogen ions (H+) produced and strength of bases depends
on number of hydroxide ions (OH-)
produced. A universal indicator (present on pH paper) is used to find strength
of acids or bases.
pH Scale:-
It is a scale to measure hydrogen
ion concentration in solution.
pH also known by seeing the color change in litmus paper.
Meaning of ‘p’ in ‘pH’ is
“potenz”, which is a German word whose meaning is “power”.
pH scale measure pH from 0
(very acidic) to 14 (very alkaline).
pH of Neutral Solution is 7
pH of Acidic Solution is less
than 7
pH of Basic Solution is more
than 7
How to Measure PH of Acids and Bases ?
You can measure pH of acids and bases with the help of litmus paper, pH paper and pH meter. To know pH of any substance watch below pH experiment conducted by the Chemistry Notes Info.
What is acid rain?
If pH of rain water is below
5.6 on pH scale than, that rain is called as acid rain.
Some Naturally Occurring Acids:-
Natural Source
|
Acid
|
Vinegar
|
Acetic Acid
|
Orange
|
Citric Acid
|
Tamarind
|
Tartaric Acid
|
Tomato
|
Oxalic Acid
|
Sour Milk (Curd)
|
Lactic Acid
|
Lemon
|
Citric Acid
|
Ant Sting
|
Methanoic Acid
|
Nettle Sting
|
Methanoic Acid
|
Common Salt:-
Common salt is very important
raw material for production of other daily use material.
Sodium Hydroxide:-
Sodium Hydroxide is obtained
by passing electricity through aqueous solution of sodium chloride (brine).
Process is known as Chlor-Alkanization.
2NaCl (aq) + 2H2O
(l) ----> 2NaOH (aq) + Cl2
(g) + H2 (g)
Bleaching Powder (CaOCl2):-
Bleaching Powder is obtained
by reaction between chlorine (Cl2) and dry slaked lime [Ca(OH)2].
Ca(OH)2 + Cl2
-----> CaOCl2 + H2O
Use of Bleaching Powder:-
·
For bleaching
wood pulp in paper industry.
·
For bleaching
washed clothes in laundry.
·
For bleaching
cotton and linen in textile industry.
·
Used as oxidizing
agent in chemical industry.
·
Used as
disinfectant for drinking water to kill germs.
Baking Soda:-
Chemical name of baking soda
is sodium hydrogen carbonate (NaHCO3). It is obtained by reaction
between Sodium Chloride (NaCl), Water (H2O), Carbon Dioxide (CO2)
and Ammonia (NH3).
NaCl + H2O + CO2
+ NH3 ----> NH4Cl (Ammonium Chloride) + NaHCO3 (Sodium
Hydrogen Carbonate)
Uses of Sodium Hydrogen Carbonate:-
·
To produce baking
powder {mixture of baking soda + mild edible acid (like tartaric acid)}
·
Used to produce
antacids (neutralize access acid in stomach to provide relief from acidity)
·
Used in soda acid
fire extinguishers
Washing Soda:-
Washing soda is obtained by
heating baking salt (Sodium Hydrogen Carbonate) and recrystallization of Sodium
Carbonate produced above.
2NaHCO3 (Sodium
Hydrogen Carbonate) + Heat --------> Na2CO3 (Sodium Carbonate) + H2O
+ CO2
Na2CO3
+ 10H2O --------> Na2CO3.10H2O
Uses of Washing Soda:-
·
Used in glass,
soap and paper industries
·
Used in
preparation of sodium compounds like borax
·
Used as cleaning
agent
·
Used for removal
of permanent hardness of water
Crystal of Salt:-
Presence of fixed no. of
water molecules in one formula unit of salt is called as water of
crystallization.
·
Copper sulphate
crystals with water molecule (CuSO4.5H2O) are blue in
color, while
·
Copper sulphate crystals without water
molecule (CuSO4) are white in color.
Plaster of Paris:-
Plaster of Paris is obtained
by heating gypsum (CaSO4.2H2O) at 373K.
CaSO4.2H2O
(Gypsum) + Heat ----> CaSO4.1/2H2O (Plaster of Paris) + 3/2H2O
Uses of Plaster of Paris:-
·
Used by
orthopedic doctors for supporting fractured bones.
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