[precious]

Aceylene gas is a mixture of C2H2 and O2. The reaction is: 2C2H2 + 5O2 -- 4CO2 + 2H2O.. Imagine that you have a 5.5L and a 2.5L gas tank. you need to fill one tank with o2 and the other with acetylene to use in conjunction with the welding torch. If you fill the largest with the oxygen to a pressure of 115 atm, to what pressure should you fill the acetylene tank to ensure that you run out of each gas at the same time? i tried using Boyles Law (Pi x Vi = Pf x Vf)but the answer was incorrect.

[Lt.Pliskin]

Hints:  Mole ratio, Ideal gas equation