# Do you adjust gas flow rate (SCCM) to volume of chamber?

If I am carrying out a reaction by flowing 200 SCCM of a gas in a 20mm diameter pipe at 100mm length, if I change the pipe diameter to 10mm:

1. Do I adjust the mass flow rate of the gases?
2. If so, how do you calculate this?

Thank you for helping. Looking to learn. Cheers

$$Flow = \frac {P_1 -P_2}{R} \quad, \ R = \frac{8\eta*L}{\pi*r^4} \quad \eta = viscosity$$