CHEMISTRY COMMUNITY

2A + 1B ---> 3C

If one mole of A is mixed with one mole of B which is the limiting reactant?
How much of B would be used?
What is the maximum amount of product that can be produced?

I'm having trouble understanding how A would end up being the limiting reactant if there are fewer moles of B. Could someone walk me through this one? Thanks!

A is the limiting reactant because it takes twice as many moles of A, when compared to B, to produce the same amount of C due to their coefficients. If 1 mol of A is used, only 0.5 mol of B is used, again, because of their coefficient ratio of 2 mol A: 1 mol B. Essentially, you should always look at the coefficients of reactants because depending on which reactant has a higher one, it suggests it takes more of that specific reactant to produce whatever is on the product side of a reaction. But, of course, always consider how many moles of reactant there are and use dimensional analysis to solve for moles of product produced if each reactant is completely used.

If 1 mole of A reacted with 1 mole of B, but the reaction requires *2* moles of A to react with every 1 mole of B, then there is a limited amount of A present and that limits the amount of product that can be formed. The reaction would still proceed, with 1 mole of A reacting with 0.5 mole of B (the ratio is still 2:1 for A:B) but there would only be 1.5 moles of product (C) formed, which is because there isn't enough of A to form the 3 moles of C.