What is the acetylene critical point described in the material?

• A. 28 psi @ 21 degrees C
• B. 15 psi @ 21 degrees C
• C. 28 psi @ 0 degrees C
• D. 10 psi @ 21 degrees C

Answer: (A)

Acetylene’s stability depends on both pressure and temperature, and there’s a boundary where it can become unstable and decompose if pressure is too high for the given temperature. At typical room temperature (about 21°C), this boundary is around 28 psi. So the described acetylene critical point is 28 psi at 21°C. The other options don’t fit because they pair the same pressure with temperatures that aren’t the room-temperature condition described, or they use a different temperature altogether.