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Acetylene torches are used for welding. These torches use a mixture of acetylene

ID: 533815 • 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 7.00 L gas tank and a 4.00 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? Assume ideal behavior for all gases.

Express your answer with the appropriate units.

Explanation / Answer

2 moles of acetylene gas requires 5 moles of oxygen gas

Uaing ideal gas law , lets determine the number of moles of oxygen, temperature = 298 k

PV =nRT

105 × 7 = n × 0.0821 × 298

n = 30.042 moles

So 30.042 moles of oxygen will require (30.042 × 2) / 5 = 12.02 moles of acetylene.

Using ideal gas law,

PV = nRT

P × 4 = 12.02 × 0.0821 × 298

P = 73.5 atm

So the pressure of acetylene gas must be 73.5 atm