Introduction - Chemical Reactions

The gas which reacts with oxygen to give a neutral liquid.

Give reason for the following:

Silver salts are kept in dark coloured bottles.

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.

Explain the term 'chemical reaction' with special reference to - 'reactants' & 'products'.