Class 10 Chemistry

Acid Base and Salt

Base: Base is bitter in taste and feels soapy on touch. A base turns red litmus paper blue.

Sodium hydroxide (caustic soda), calcium hydroxide, sodium carbonate (washing soda), lime (Calcium oxide), potassium hydroxide (caustic potash), etc. are examples of base.

Types of base: Base can be divided in two types – Water soluble and water insoluble.

The ionic salt of alkali and alkaline earth metals are soluble in water. These are also known as alkali. For example – sodium hydroxide, magnesium hydroxide, calcium hydroxide, etc. Alkali is considered as strong base.

Reaction of Base with Metals:

When alkali (base) reacts with metal, it produces salt and hydrogen gas.

Alkali + Metal ⇨ Salt + Hydrogen

Example: Sodium hydroxide gives hydrogen gas and sodium zincate when reacts with zinc metal.

2NaOH + Zn ⇨ Na2ZnO2 + H2

Sodium aluminate and hydrogen gas are formed when sodium hydroxide reacts with aluminium metal.

2NaOH + 2Al + 2H2O ⇨ 2NaAlO2 + 2H2

Reaction of base with oxides of non-metals:

Non-metal oxides are acidic in nature. For example; carbon dioxide is a non-metal oxide. When carbon dioxide is dissolved in water it produces carbonic acid.

Therefore, when a base reacts with non-metal oxide both neutralize each other resulting respective salt and water are produced.

Base + Non-metal oxide ⇨ Salt + Water

Example: Sodium hydroxide gives sodium carbonate and water when it reacts with carbon dioxide.

2NaOH + CO2 ⇨ Na2CO3 + H2O

Calcium hydroxide gives calcium carbonate and water when it reacts with carbon dioxide.

Ca(OH)2 + CO2 ⇨ CaCO3 + H2O

Neutralisation Reaction:

An acid neutralizes a base when they react with each other and respective salt and water are formed.

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 chloride and water are formed when hydrochloric acid reacts with sodium hydroxide (a strong base).

HCl + NaOH ⇨ NaCl + H2O

In similar way, calcium chloride is formed along with water when hydrochloric acid reacts with calcium hydroxide (a base).

2HCl + Ca(OH)2 ⇨ CaCl2 + 2H2O

Sodium sulphate and water are formed when 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

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

Example: 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 sulphuric acid reacts with zinc oxide, zinc sulphate and water are formed.

H2SO4 + ZnO ⇨ ZnCl2 + H2O

When hydrochloric acid reacts with aluminium oxide, aluminium chloride and water are formed.

Al2O3 + 6HCl ⇨ 2AlCl3 + 3H2O

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