Imagine that you have a 5.50 L gas tank and a 3.50 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 155 atm , to what pressure should you fill the acetylene tank to ensure that you run out of each gas at the same time? Assume ideal behavior for all gases.

1 answer

2C2H2 + 5O2 ==> 4CO2 + 2H2O

Use PV = nRT for O2. Plug in 155 atm for P, V = 5.5L, Assume any value for T(in kelvin) and use your chosen value for T throughout. Solve for n = number of mols O2.

Knowing you need that many mols O2, use the coefficients in the balanced equation to convert mols O2 to mols C2H2.

Then use PV = nRT for the C2H2 tank and solve for P. Use the same value of T you used in the first calculation.