CBSE
Class 10
Class 12
The base is a substance which releases hydroxide ions when dissolved in water.
Indicators - Indicators are substances which indicate the acidic or basic nature of the substance/solution by their colour change.
Types of Indicators:
A universal indicator is a special kind of indicator which is used to measure the strength of acidity or alkalinity. It is prepared by several organic indicators of different of different colours. It is found in green blue solution or in the form of yellow litmus paper.
The colour of some acid-base indicators in the acidic and basic medium are given below.
Indicators |
Litmus |
Phenolphthalein |
Methyl Orange |
Acid |
Blue to Red |
Colorless |
Red color |
Base |
Red to Blue |
Pink Color |
Yellow color |
Salt |
No change |
Neutral |
No change |
Neutralisation Reaction
When an acid and base react with each other they neutralize each other and given salt and water
Acid + Base → Salt + Water
Since in the reaction between acid and base both neutralize each other, hence it is also known as neutralization reaction.
Example:
Sodium sulphate and water are formed when a sulphuric acid reacts with sodium hydroxide (a base).
H2SO4 + 2NaOH → Na2SO4 + 2H2O
In similar way, when nitric acid reacts with sodium hydroxide, sodium nitrate and water are formed.
HNO3 + NaOH → NaNO3 + H2O
The reaction of the acid with metal
Acids give hydrogen gas along with respective salt when they react with a metal.
Metal + Acid → Salt + Hydrogen
Example:
Hydrogen gas and zinc chloride are formed when hydrochloric acid reacts with zinc metal.
Zn + 2HCl → ZnCl2 + H2
Hydrogen gas and sodium chloride are formed when hydrochloric acid reacts with sodium metal.
2Na + 2HCl → 2NaCl + H2
The reaction of metal with a base
When alkali (base) reacts with metal, it produces salt and hydrogen gas.
Alkali + Metal → Salt + Hydrogen
Example:
Sodium aluminate and hydrogen gas are formed when sodium hydroxide reacts with aluminium metal.
2NaOH + 2Al + 2H2O → 2NaAlO2 + 2H2
Sodium hydroxide gives hydrogen gas and sodium zincate when reacts with zinc metal.
2NaOH + Zn → Na2ZnO2 + H2
The reaction of acids with metal carbonate:
Acids give carbon dioxide gas and respective salts along with water when they react with metal carbonates.
Metal carbonate + Acid → Salt + Carbon dioxide + Water
Examples:
Sulphuric acid gives calcium sulphate, carbon dioxide gas, calcium sulphate and water when it reacts with calcium carbonate.
CaCO3 + H2SO4 → CaSO4 + CO2 + H2O
Reaction of acid with hydrogen carbonates (Bicarbonates)
When an acid reacts with hydrogen carbonates, it gives carbon dioxide gas, respective salt and water.
Acid + Metal hydrogen carbonate → Salt + Carbon dioxide + Water
Examples:
Hydrochloric acid gives carbon dioxide, sodium chloride and water when it reacts with sodium bicarbonate.
NaHCO3 + HCl → NaCl + CO2 + H2O
The reaction of Base with metal hydrogen carbonates/Metal Carbonate
No reaction will occur when base reacts with hydrogen carbonates/Metal Carbonate.
Base + Hydrogen Carbonates/Metal Carbonate → No reaction
Reaction of acid with metal oxides:
Metal oxides are basic in nature. Thus, when an acid reacts with a metal oxide both neutralize each other. In this reaction, respective salt and water are formed.
Acid + Metal → Oxide Salt + Water
Calcium is a metal, thus calcium oxide is a metallic oxide which is basic in nature. When
an acid; such as hydrochloric acid; reacts with calcium oxide, neutralization reaction takes
place and calcium chloride; along with water; is formed.
2HCl + CaO → CaCl2 + H2O
Similarly, when a sulphuric acid reacts with zinc oxide, zinc sulphate and water are formed.
H2SO4 + ZnO → ZnCl2 + H2O
Base reacts with Non-metallic oxide and produces salt and water.
Ca(OH)2(s) + CO2(g) → CaCO3(s) + H2O(g)