This may be a stupid question, but I cant figure it out... So I hoping someone can help me

Question 2:
Ammonia is a gas for which reliable analytical methods are available to determine its concentration in other gases. To measure flow in a natural gas pipeline, pure ammonia gas is injected into the pipeline at a constant flow rate of 72.3 kg/min for 12 minutes. Five miles downstream from the injection point, the steady state ammonia concentration is found to be 0.382 weight percent. The gas upstream from the ammonia injection point contains no measurable ammonia. What is the flow rate of the natural gas in the pipeline in kg/h?

PLus i can't really visualize whats going on :(

Thnx



midterm tom!

Mass in = mass out

Draw a control volume with arrows representing the different streams: one for the injection, and one for the gas flow going in, and one for the total stuff going out. Then be sure to do a balance on the mass, not just the concentration.

hope that helps a bit, and good luck on your midterm!