What is the term used to describe the reagent that we DO know the concentration of?

This classification of drug typically changes the brain's chemistry and reduces its ability to create its own endorphins.

In the millikan oil drop experiment they determined that every drop had a charge which was a while number multiple of -1.60x10^-19. if a drop has a total charge of -9.60x10^-19 then how many excess electrons are contained within the drop?

What happens to the average kinetic energy of a gas when the particles of the gas collide against each other at a constant temperature and volume? explain your answer.