Molar Flow Rate is a measure of the amount of substance (the number of molecules) that passes through a given area perpendicular to the flow in a given time. Typically this area is constrained, for example a section through a pipe, but it could also apply to an open flow.
Applicable units are those of quantitykind:MolarFlowRate
https://www.sciencedirect.com/topics/engineering/molar-flow-rate
https://cdd.iec.ch/cdd/iec61987/iec61987.nsf/ListsOfUnitsAllVersions/0112-2---62720%23UAD122
Molar Flow Rate is a measure of the amount of substance (the number of molecules) that passes through a given area perpendicular to the flow in a given time. Typically this area is constrained, for example a section through a pipe, but it could also apply to an open flow.