Question

Consider the following reaction: A + B → C
a)When A and B are reacted in such a way that A is completely consumed 3 moles of C are obtained
b) When the reaction was carried out using different amounts of moles for A, and keeping the amount of B as before, and making sure that B reacted completely- 5 moles of C were obtained. Please, indicate which is the limiting reactant in each case.

Answer 1

a) A - it is completely consumed
b) B - B reacted completely

Answer 2

in a) we are getting 3 moles of C and since A is reacting completely therefore we surely have 3 moles of A. Now, in b) we r getting 5 moles of C, and since B is reacting completely therefore we have 5 moles of B. but we aren't changing the moles of B therefore we also have 5 moles of B in a).
Now, compare, in a)- limiting reagent is A (3 moles)
in b) in case the moles of A are more than 5 we have a limiting reagent as B, however if no of moles of A equals 5 then we have no limiting reagent.