Verified answer

let's start by writing a balanced equation...

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

now.. those coefficients can be read as molecule or as mole ratios. But for the special case of gases at the same temperature and pressure, they can also be read as "volume" ratios. Why? because PV = nRT.. V/n = RT/P.. at constant RT/P.. V/n = a constant.. ie.. (V/n) C2H2 = (V/n) O2 ----> nO2 / nC2H2 = VO2 / VC2H2.. get it? mole ratio = volume ratio for ideal gases at constant T and P.

**********

so what does all that mumbo jumbo mean?

2 moles C2H2 react with 5 moles O2

AND

2 liters C2H2 react with 5 liters O2...

so.. ratio of O2 to C2H2 must be 5:2

2C2H2 + 5O2 ====> 4C02 + 2H20

You could write it lilke this

C2H2 + 2.5 02 =====> 2C02 + H20

That means that 1 mole of C2H2 needs 2.5 moles of 02.

So the flow rate needs to be 1 L C2H2 to 2.5 L per minute.