Question

Answer the following:

(1) What is the importance of a chemical equation?

(2) What do you observe when H₂S gas is passed through Cadmium Chloride solution? Name the type of reaction.

(3) What do you understand by the term “Redox Reactions” Explain with one example.

(4) What is corrosion? Do gold ornaments corrode? Justify.

Answer 1

(1) A chemical equation can convey the following information:

• Reactants and products involved in the reaction

• Relative masses of reactants and products

• Relative number of reactants and products participating in the reaction

• Symbols and formulae of all the substances involved in the reaction

• Physical states of reactants and products

(2) When hydrogen sulphide gas is passed through cadmium chloride solution, the colour of the solution turns into yellow due to the formation of cadmium sulphide.

This is double displacement reaction.

(3) Redox reaction is a reaction in which both oxidation and reduction reactions take place simultaneously.

For example:

Here Mg gets oxidized to Mg²⁺ while oxygen gets oxidized to O^2-.

(4) Corrosion: The slow process of decay of metal due to the effect of air, moisture and acids on it is known as corrosion.

For example: Due to the effect of moisture, a layer of reddish brown colour is deposited over the iron surface, which is called rust.

Gold ornaments do not corrode because gold is a least reactive metal. It does not react with air, moisture, sweat, or ordinary pollutants in the air or water.