limiting reactants, and excess reagents--chemistry?

Question

plants use CO2, and H2O in Photosynthisis to make glucose (C6 H12 O6). if a plant has 88 grams of CO2, and 64 grams of H2O determine the following:

limiting reactant


excess reagent and mass in excess


mass of glucose produced






this one realy stumped me, I got 89.318 grams of glucose produced, and i cant figure out which is the limiting reactant and excess reagent.

thanks to whoever answers

Answer 1

You must first figure out how much glucose will be produced under two conditions:

a.) The CO2 reacts completely
b.) The H2O reacts completely

In a limiting reagent problem, you need to consider that, in order for one reagent to react fully, there must be enough of the other reagent for it to react with. Invariably, you'll have some reagent left over, and that will be your "excess reagent".

So, when you look at your answers for a and b, which answer provides you with the least glucose? The one that gives you that answer will be your "limiting reagent". Why? Because the reaction would ideally continue further, but you've run out of your limiting reagent, and you need both reagents present for a reaction to take place.

Hope that helps!