Imagine that you have a 7.00 L gas tank and a 4.50 L gas tank. You need to fill one tank with oxygen and the other with acetylene to use in conjunction with your welding torch. If you fill the larger tank with oxygen to a pressure of 136 bar , to what pressure should you fill the acetylene tank to ensure that you run out of each gas at the same time? Assume ideal behaviour for all gases.

1 answer

2C2H2 + 5O2 ==> 4CO2 + 2H2O
Use PV = nRT and solve for mols oxygen.
Use the coefficients in the balanced equation to convert mols O2 from your first calculation above to mols C2H2.
Then use PV = nRT to convert mols C2H2 to pressure. Post your work if you get stuck.