Extra credit, Monday, Sept. 15

Monday's lecture was basically a definition of limiting and excess reagents,

and how to distinguish between the two in a chemical reaction. By first

determining how many moles of each reactant you have and then determining

the molar ratio between the two, it is relatively easy to tell which

reactant will be completely used up (the limiting reagent) and which will be

left over (the excess reagent) using stoichiometry:

Mol Subst. A x molar ratio (B/A) = Mol subst. B needed for reaction.

If "mols subst. B needed" is less than the amount you started with, then B

is in excess and A is the substance that limits how far the reaction can go.

If "mol B needed" is more than you started with, the opposite is true.

Professor White's explanation of how to determine limiting and excess

reagents had a few more steps, and while it still works well, I find that

from a common sense standpoint this method works out well... it just

involves more reasoning than actual paperwork.