Explain what happens when Carbon dioxide is bubbled through lime water (give equation).

Explain what happens when Silver articles become black after some time (give equation).

Explain: All displacement reactions are not called double displacement reactions(give equation).

Balance the following equation:

${\mathrm{BaCl}}_2+{\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3\to {\mathrm{BaSO}}_4+{\mathrm{AlCl}}_3$

Balance the following equation:

${\mathrm{Fe}}_2{\mathrm{O}}_3+\mathrm{Al}\to {\mathrm{Al}}_2{\mathrm{O}}_3+\mathrm{Fe}$

Balance the following equation:

${\mathrm{C}}_2{\mathrm{H}}_6+{\mathrm{O}}_2\to {\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}$

The reaction which proceeds by the evolution of heat is known as _____ reaction.