When copper turnings are added to silver nitrate solution, a blue coloured solution is formed after some time. It is because copper:
(i) Displaces silver from the solution
(II) Forms a blue colored complex with ${\mathrm{AgNO}}_3$
(III)Is oxidized to ${\mathrm{Cu}}^{2+}$
(IV)Is reduced to ${\mathrm{Cu}}^{2+}$ 

Calcium oxide reacts vigorously with water to produce slaked lime.

${\mathrm{CaO}}_{\left(\mathrm{s}\right)}+{\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{l}\right)} \to \mathrm{Ca}{\left(\mathrm{OH}\right)}_{2\left(\mathrm{aq}\right)}$

This reaction can be classified as:

(A) Combination reaction        (B) Exothermic reaction

(C) Endothermic reaction        (D) Oxidation reaction

Which of the following is the correct answer?

In a double displacement reaction such as the reaction between sodium sulphate solution and barium chloride solution:

(A) exchange of atoms takes place.

(B) exchange of ions takes place.

(C) a precipitate is produced.

(D) an insoluble salt is produced.

The correct option is:

Assertion ($\mathrm{A}$): A primary succession is more common than secondary succession.

Reason ($\mathrm{R}$): Biogeochemical cycling is absent in secondary succession.

Fill in the blank with the most appropriate option given below.

We should give everyone training in citizenship, but we have______this aspect till now.

When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is obtained and the sulphuric acid so formed remains in the solution. The reaction is an example of a :

Match the following lists:

The correct match is