Question

4. Carbon dioxide is used for extinguishing fires caused by petroleum products but not fires caused by metals like Na or Mg. Explain.

Answer 1

• Carbon dioxide (CO₂) is the best extinguisher for fires involving electrical equipment and combustible fuels such as petroleum.
• CO₂, being heavier than oxygen, acts as a blanket over the flames.
• The fire is controlled because there is no contact between the fuel and the oxygen.
• Fires caused by metals like sodium $\left(\mathrm{Na}\right)$ or magnesium $\left(\mathrm{Mg}\right)$ are not extinguished by Carbon dioxide because they are active metals and they react with Carbon dioxide to form corresponding oxides.
• The reaction of magnesium with Carbon dioxide is given as:
• $\underset{\mathrm{Magnesium}}{2\mathrm{Mg}}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2}\to \underset{\mathrm{Magnesium}\mathrm{oxide}}{2\mathrm{MgO}}+\underset{\mathrm{Carbon}}{\mathrm{C}}$