Imagine that you have a 6.50 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 105 atm , to what pressure should you fill the acetylene tank to ensure that you run out of each gas at the same time

We have to fill the acetylene tank with a pressure of 60.67 atm to ensure that you run out of each gas at the same time

Explanation:

Step 1: Data given

Volume of  tank 1 = 6.50 L = oxygen

Volume of tank 2 = 4.50 L = acetylene

Pressure in the oxygen tank = 105 atm

Step 2: The balanced equation

2 C2H2 + 5 O2 → 4 CO2 + 2 H2O

For 2 mol C2H2 we need 5 moles O2 to produce 4 moles CO2 and 2 moles H2O

 Step 3: Calculate the pressure of the acetylene tank

For 2 mol C2H2 we need 5 moles O2 to produce 4 moles CO2 and 2 moles H2O

This means for each 5 moles O2 we have 2 moles acetylene

Pressure (105 atm) * (2/5) * (6.50 / 4.50) = 60.67 atm

We have to fill the acetylene tank with a pressure of 60.67 atm to ensure that you run out of each gas at the same time