Question

In foam type extinguisher ______ is present in bottle.

• A. $N{a}_{2}C{O}_3$
• B. $A{l}_2(S{O}_4{)}_3$
• C. $Al(OH{)}_3$
• D. $N{a}_{2}S{O}_4$

Answer 1

The correct option is B $A{l}_2(S{O}_4{)}_3$

Aluminium sulfate reacts with sodium bicarbonate to which foam stabilizer has been added, producing carbon dioxide for fire extinguishing foams: $A{l}_2(S{O}_4{)}_3+NaHC{O}_3\to Al(OH{)}_3+N{a}_{2}S{O}_4+C{O}_2$

The carbon dioxide is trapped by the foam stabilizer and creates a thick foam that will float on top of hydrocarbon fuels and seal off access to atmospheric oxygen, smothering the fire.

Chemical foam was unsuitable for use on polar solvents such as alcohol, as the fuel would mix with and break down the foam blanket. Aluminum sulfate will remain in bottle because $C{O}_2$ from above reaction will release from sodium bicarbonate.

Thus Option B is correct.