Acetylene becomes unstable if compressed to more than 15 psi.

• A. True
• B. False
• C. Depends on cylinder
• D. Depends on ambient temperature

Answer: (A)

Acetylene’s stability is highly pressure-dependent. When acetylene gas is compressed beyond a small limit, it can decompose violently, which is why pure acetylene is not stored or used as a high-pressure gas. To handle this safely, acetylene is stored dissolved in acetone within a porous, cancellous cylinder packing, keeping the gas stable at higher pressures while still allowing regulated delivery. In practice, the cylinder pressure can be relatively high, but the acetylene remains in solution and controlled by the design of the cylinder and the regulator.

That’s why the statement is true: acetylene becomes unstable when compressed beyond about 15 psi if it were present as a free gas. The other options don’t capture this fundamental stability issue—the cylinder type doesn’t change the basic instability threshold, and ambient temperature is a secondary factor rather than the defining limit.