Give one example where supplying pressure is necessary for a chemical reaction.

Representation of the results of a chemical change - is a chemical equation.
For the equation: 

${\mathrm{FeCl}}_3 + 3{\mathrm{NH}}_4\mathrm{OH} \to 3{\mathrm{NH}}_4\mathrm{Cl} + \mathrm{Fe}(\mathrm{OH}{)}_3\downarrow$ .

Answer the following:
(a) Write the word equation for the above molecular equation.
(b) Is the equation given above a balanced equation. Give reasons.
(c) Name the reactants and the products in the above equation.
(d) What are the indications of the arrow between the reactants and the products and of the arrow pointing downwards at the end.

Give word equations for the following chemical reaction and give the name of the product formed.
$\mathrm{Zn}+2\mathrm{HCl}\to {\mathrm{ZnCl}}_2+{\mathrm{H}}_2$

Give word equations for the following chemical reaction and give the name of the product formed.

$\mathrm{CuO}+{\mathrm{H}}_2{\mathrm{SO}}_4 \to {\mathrm{CuSO}}_4+{\mathrm{H}}_2\mathrm{O}$

Give word equation for the following chemical reaction and give the name of the product formed.

$\mathrm{Zn}+\mathrm{S} \to \mathrm{ZnS}$

Give word equations for the following chemical reaction and give the name of the products formed.

${\mathrm{ZnCO}}_3 \stackrel{∆}{\to }\mathrm{ZnO}+{\mathrm{CO}}_2$

Give a word equation for the following chemical reaction and give the name of the products formed.

${\mathrm{NH}}_3+\mathrm{HCl}\to {\mathrm{NH}}_4\mathrm{Cl}$

The black residue obtained on heating copper carbonate.