Why should an equation be balanced? Explain your answer by giving a simple equation.

Balance the following equations:

$\mathrm{Fe}+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{Fe}}_3{\mathrm{O}}_4+{\mathrm{H}}_2$

Balance the following equations:

$\mathrm{Ca}+{\mathrm{N}}_2\to {\mathrm{Ca}}_3{\mathrm{N}}_2$

Balance the following equation:

$\mathrm{Zn}+\mathrm{KOH}\to {\mathrm{K}}_2{\mathrm{ZnO}}_2+{\mathrm{H}}_2$

Balance the following equation:

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

Balance the following equation:

$\mathrm{PbO}+{\mathrm{NH}}_3\to \mathrm{Pb}+{\mathrm{H}}_2\mathrm{O}+{\mathrm{N}}_2$

Balance the following equation:

${\mathrm{Pb}}_3{\mathrm{O}}_4\to \mathrm{PbO}+{\mathrm{O}}_2$

Balance the following equation:

$\mathrm{PbS}+{\mathrm{O}}_2\to \mathrm{PbO}+{\mathrm{SO}}_2$

Balance the following equation:

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