Define double displacement reaction and give one example of each of the following types of this reaction in which
(i) a yellow precipitate is formed
(ii) a black precipitate is formed
(iii) a gas is liberated
(iv) a white precipitated is formed
(v) two other solutions are formed.

Define double displacement reaction and give one example of the following type of the reaction in which a black precipitate is formed.

 Explain the following:

$\mathrm{Cu} + 2{\mathrm{AgNO}}_3 \to \mathrm{Cu}({\mathrm{NO}}_3{)}_2 + 2\mathrm{Ag}$ is a redox reaction.

In the reaction $2\mathrm{Na} + {\mathrm{O}}_2\to 2\mathrm{NaO}$, identify the substance which loses electrons and is oxidized.

In the reaction $2\mathrm{Na} + {\mathrm{O}}_2\to 2\mathrm{NaO}$, identify the substance which gains electrons and is reduced.