Madhya Pradesh Police Exam Model Paper 4

The correct answer is  Cutting the supply of air.

• The reaction of acids with metal hydrogen carbonates is used in the fire extinguishers which produce carbon dioxide.
• Soda-acid fire extinguishers consist of sodium bicarbonate and sulphuric acid.
• The chemical reaction that takes place in the soda-acid fire extinguisher is as follows:
  • $2{\mathrm{NaHCO}}_3+\mathrm{H}\_2{\mathrm{SO}}_4\to {\mathrm{Na}}_2{\mathrm{SO}}_4+2{\mathrm{H}}_2\mathrm{O}+2{\mathrm{CO}}_2$
• This extinguisher is used for class A fires.
• The working principle of Soda-acid fire extinguishers(any fire extinguisher) is based on the following three conditions:
  • Cooling the combustible material below its ignition temperature.
  • Cutting off the supply of air.
  • Cooling the combustible material and at the same time cutting the supply of air.