Acetylene torches are used for welding. These torches use a mixture of acetylene
ID: 922170 • Letter: A
Question
Acetylene torches are used for welding. These torches use a mixture of acetylene gas, C2H2, and oxygen gas, O2 to produce the following combustion reaction:
2C2H2(g)+5O2(g)4CO2(g)+2H2O(g)
Imagine that you have a 7.00 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 125 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.
Explanation / Answer
Given that
2C2H2(g) + 5O2(g) 4CO2(g) + 2H2O(g)
Oxygen:
Volume of larger tank V1 = 7.00 L
Pressure P1 = 125 atm
no of moles of oxygen in the above balanced equation n1 = 5
Acetylene:
Volume of small tank V2 = 3.50 L
Pressure P2 = ? atm
no of moles of acetylne in the above balanced equation n2 = 2
From Ideal gas equation.
P1V1/n1 = P2V2/n2
P2 = ( P1V1/n1) (n2/V2)
= (125 atm x 7.00 L / 5 moles) (2 moles/ 3.50 L)
= 100 atm
Pressure of acetylene gas = 100 atm
Therefore, at 100 atm pressure acetylene tank should be filled.