<p>i was confused about one thing regarding limiting reactions on our lab we did. </p>
<p>if you perform a reaction between Al and CuCl2 hydrate, to find which one is the limiting reactant, do you just convert the grams of aluminum to grams of copper and see what the theoretical yield should have been? because you dont have the yield by CuCl2 to compare it to so what do you do?</p>
<p>or do you just put that because aluminum was left over in the reaction, it must the excess?
and dont show any work?</p>
<p>If you know what the products are, then you can balance the reaction to find out how many mols of each of the reactants you need.</p>
<p>Then, convert the grams of Al and grams of of CuCl2 2-hydrate to mols. </p>
<p>Then, pick either reactant use the ratio between the reactants to determine if there are enough mols of the other. (ie if the ratio is 2Al to 3 CuCl2, let's say you pick Al. And let's say you start with 1 mol of Al. This means you need 1 x (3/2) mols of CuCl2. Check to see whether you started with 3/2 mols of CuCl2. If there were fewer than 3/2 mols, then it is the limiting reactant. If you started with more than 3/2, then it is the excess reactant and Al is the limiting)</p>