[scientizscht (OP)]

Hello!

There is a gas flowing uniformly at 3.5L/s in a cylindrical pipe of 15cm diameter. Imagine an 1ml cube somewhere inside that pipe with imaginary boundaries. Imagine that at time t1, the cube is filled with gas. After one second, at time t2, some gas has gotten out of the cube and some new gas has entered the cube. How much gas would pass through that cube in 1 sec?

Thanks!

[Bored chemist]

Calculate the area of the pipe from the diameter.
From that and the flow rate you can calculate the average velocity and from that you can tell how long it takes (on average) for the current to sweep 1 cm.

However, the flow rate across the pipe will vary a lot so the amount of gas flowing through your cube each second will also vary a lot.
This might help

http://hyperphysics.phy-astr.gsu.edu/hbase/pfric.html

Why do you ask?