Question

Which of the following acid is used in fire extinguishers?

• A. Hydrochloric acid
• B. Sulphuric acid
• C. Nitric acid
• D. Oxalic acid

Answer 1

Answer: (B)

Sulphuric acid

Soda-acid extinguisher uses the reaction between sodium bicarbonate solution and sulphuric acid to expel pressurized water onto a fire. The reaction takes place as follows :-

$2NaHC{O}_3+H_{2}S{O}_4\to N{a}_{2}S{O}_4+2C{O}_2+2H_{2}O$

The $C{O}_2$ formed forces the water out of the discharge and hence the device must be held in upright position.

However, such extinguisher can't be used in case of fire caused due to electricity (as water is a good conductor of electricity) and fire caused due to oil or petrol (as the oil or petrol may float over water).

Thus, the correct answer is option (B).