Question

Why potassium nitrate is not used for the preparation of oxygen in the laboratory?

Answer 1

Potassium nitrate is a solid that when heated melts and on further heating it decomposes into Potassium nitrite and Oxygen.

$\underset{\mathrm{Potassium}\mathrm{nitrate}}{2{\mathrm{KNO}}_3\left(\mathrm{s}\right)}\stackrel{∆}{\to }\underset{\mathrm{Potassium}\mathrm{nitrate}}{2{\mathrm{KNO}}_3\left(\mathrm{l}\right)}\stackrel{∆}{\to }\underset{\mathrm{Potassium}\mathrm{nitrite}}{2{\mathrm{KNO}}_2\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}$

• Hence, we see that it requires strong heating to get oxygen from Potassium nitrate.
• Also, the rate of evolution i.e., Oxygen formation is very slow in this process.
• We have other simple methods to extract oxygen gas than this.
• Thus, it is not used for the preparation of oxygen in the laboratory.