We can turn curd back into milk as it is a physical change.

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 :

Taking into consideration the relationship in the first pair, complete the second pair: 

$2{\mathrm{H}}_2+{\mathrm{O}}_2\to 2{\mathrm{H}}_2\mathrm{O}$: Combination reaction: $2\mathrm{HgO}\to 2\mathrm{Hg}+{\mathrm{O}}_2$: _____.

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:

If $0.50$ moles of ${\mathrm{BaCl}}_2$ is mixed with $0.20$ moles of ${\mathrm{Na}}_3{\mathrm{PO}}_4$ the maximum number of moles of ${\mathrm{Ba}}_3{\left({\mathrm{PO}}_4\right)}_2$ formed will be 

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?

Write a balanced chemical equation for the following:

• Reaction of lead nitrate solution with ammonium hydroxide.

The reaction of the iron nail with copper sulphate solution is a _____ reaction.