Acetylene torches are used for welding. These torches use a mixture of acetylene
ID: 959272 • 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)
Part A
Imagine that you have a 5.50 L gas tank and a 2.50 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
2C2H2(g)+5O2(g)4CO2(g)+2H2O(g)
from the balanced equation it is clear that
the ratio of the acetylene and O2 is 2:5 or
one mole of O2 required 2/5 moles of Acetylene
no of moles of O2 = 125 atm x 5.50 L = 687.5 L = 687.5 / 22.4 = 30.7 mol
from the balanced equation
no of moles of C2H2 = 2/5 (30.7) = 12.3 mol
convert in to liters = 12.3 x 22.4 = 275 L
now the pressure is 275 / 2.5 = 110 atm