Question

Complete and balance the following equations giving the conditions necessary for the reactions :

${\mathrm{KNO}}_3\to \mathrm{\_\_\_\_\_\_\_}+\mathrm{\_\_\_\_\_\_}$

Answer 1

The action of heat on potassium nitrate (${\mathrm{KNO}}_3$):

• When potassium nitrate is heated, it fuses (melts) and then decomposes into potassium nitrite and oxygen.
• The melting process is a physical change while decomposition is a chemical change.
• $$\begin{gathered} \underset{\mathrm{potassium}\mathrm{nitrate}}{{\mathrm{KNO}}_3\left(\mathrm{s}\right)}\stackrel{\mathrm{heat}}{\to }\underset{\mathrm{potassium}\mathrm{nitrate}}{{\mathrm{KNO}}_3\left(\mathrm{l}\right)}-\mathrm{physical}\mathrm{change} \\ \underset{\mathrm{potassium}\mathrm{nitrate}}{2{\mathrm{KNO}}_3\left(\mathrm{s}\right)}\stackrel{\mathrm{heat}}{\to }\underset{\mathrm{potassium}\mathrm{nitrite}}{2{\mathrm{KNO}}_2\left(\mathrm{s}\right)}+\underset{\mathrm{oxygen}\mathrm{gas}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}-\mathrm{chemical}\mathrm{change} \end{gathered}$$