Acids, Bases and Salts

Acids  These are the substance, which have sour taste and turn blue litmus red.  These are good conductor of electricity in aqueous solution.  Pickels are always kept in glass jar because acid present in them reacts with metal to produce hydrogen gas.

Bases  These are the substances, which have bitter taste and turn red litmus, blue.  They give different colours in acid and base solutions.

Study for civil services :-
These are the product of neutralisation reaction between an acid and a base.
# pH is the measure of acidity/basicity. Some Important Gases/Chemicals
Carbon Dioxide
It is an acidic oxide of carbon and is used by green plants for photosynthesis.
It does not help in burning.
Air and our breath contain carbon dioxide.

Thus, when lime water is kept in air or we pass our breath into it, the lime water turns milky.

Carbon Monoxide

Study for civil services :-
It is a neutral oxide of air and has more affinity towards haemoglobin than oxygen (about 200 times more).
That’s why in the environment of carbon monoxide – which is a non- poisonous gas – people die for the need of oxygen.
It is dangerous to sleep in an unventilated room with fire burning inside because the fire produces carbon monoxide and carbon dioxide gases.

Plaster of Paris
It is chemically calcium sulphate hemihydrate (CaSO4.1/2H2O)

and is prepared by heating gypsum – which is calcium sulphate dehydrate (CaSO4.2H2O) at 373 K.

On Mixing with water, plaster of Paris further sets into a hard solid, called gypsum.

Study for civil services :-

USES :– it is used to plaster fractured bones, for making toys, materials for decoration and for making surfaces smooth.

Portland Cement  It is a complex mixture of silicates and aluminates of calcium with small amount of gypsum. Raw materials used for the manufacture of Portland cement are limestone and clay.

 The composition of Portland cement is calcium oxide (50-60%), alumina (5-10%), and magnesium oxide (2-3%). Gypsum is added to cement to decrease its rate of setting.

Study for civil services :-
 In cement, if lime is in excess, cement cracks during setting and if lime is less, cement is of weak strength.

a mixture of sand, cement and water is used for joining bricks and plastering walls.

a mixture of gravel, sand, cement and water is used for flooring and making roads.

Reinforced Concrete Cement (RCC)—
which is concrete with steel bars and wires is used for constructing roofs, bridges and pillars


Study for civil services :-
Glass is a non-crystalline amorphous solid that is often transparent
Glass—an amorphous solid or super- cooled liquid— contains mainly silica (SiO2).
Different substances are added to obtain glass of different colours
Colour Substance Added
Red Copper oxide (CuO)
Green Chromium oxide (Cr203)
Blue Cobalt oxide (Co0)
Brown Iron oxide (Fe203)

Heavy water
Heavy water is water that contains heavy hydrogen or deuterium.

Study for civil services :-
Deuterium differs from the hydrogen usually found in water, protium, in that each atom of deuterium contains a proton and a neutron.

Heavy water may be deuterium oxide, D2O or it may be deuterium protium oxide, DHO.

Heavy water occurs naturally, although it is much less common than regular water.
Approximately one water molecule per twenty million water molecules is heavy water.

Hard Water
The water in which soluble bicarbonates of calcium and magnesium are present, is called temporary hard water

Study for civil services :-

and in which soluble sulphates and chlorides of magnesium and calcium are present is called permanent hard water.
How to Remove hardness of Water ?
The temporary hardness of water is removed by boiling or by adding calcium hydroxide, Ca(OH)2— the Clark’s process
The permanent hardness of water is removed by adding sodium carbonate (Na2CO3), or calgon (sodium hexametaphosphate, Na2[Na4(P03)