A stain is made up of molecules that do not have charged regions. What soap/solvent combination should I use?Are there multiple?

The answer is below

Explanation:

Yes, there are multiple combinations.

Firstly, a solvent or soap combination could be used as a polar solvent with soap. In this way, the nonpolar region of the soap molecules would mix directly with the stain while the solvent would surround the soap-stain micelle.

Secondly, another method or way is to have a combination of a nonpolar solvent with no soap. In this method, however, it is the solvent that would mix directly with the stain.

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.