What are the limitation of chemical reaction equation?

Write down the balanced chemical equation for the following equation:

Hydrogen plus oxygen produces water

Write down the balanced chemical equation for the following equation:

Carbon plus oxygen produces carbon dioxide

Write down the balanced chemical equation for the following equation:

Hydrogen plus chlorine produces hydrogen chloride

Write down the balanced chemical equation for the following equation:

Aluminium plus chlorine produces ammonium chloride.

Write down the balanced chemical equation for the following equation:

Hydrogen plus nitrogen produces ammonia

Balance the given equation

$\mathrm{Zn}+\mathrm{HCl}\to {\mathrm{ZnCl}}_2+{\mathrm{H}}_2$

Balance the following chemical equation::

 ${\mathrm{P}}_4+{\mathrm{O}}_2\to {\mathrm{P}}_2{\mathrm{O}}_5$