Friday, 23 October 2015

10 Class - Acids, Bases and Salts part-2

10th Class Chapter- Acids Bases and Salts

 pH Scale:-

It is a scale to measure hydrogen ion concentration in solution.
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

 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
Acetic Acid
Citric Acid
Tartaric Acid
Oxalic Acid
Sour Milk (Curd)
Lactic Acid
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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