2. What is the percent yield of Mg3N2 if 73.9 g of Mg reacts with 31.6 g of N2 to produce 79 g of Mg3N2 according to the following chemical reaction? (Reaction may or may not be balanced.)

Question

mg+n2=Mg3N2

Answer 1

This is a limiting reagent problem. You know that because amounts are given for BOTH reactants.
3Mg + N2 ==> Mg3N2
Convert 73.9g Mg to mols. mol = grams/atomic mass.
Do the same for 31.6 g N2.

Using the coefficients in the balanced equation, convert mols Mg to mols Mg3N2.
Do the same for mols N2 to mols Mg3N2.
It is likely that the two values for mols Mg3N2 will not agree which means one of them is not right; the correct value in limiting reagent problems is ALWAYS the smaller value and the reagent producing that value is the limiting reagent.

Use the smaller value and convert mol to grams. g = mols x molar mass. This is the theoretical yield (TY).
%yield = (actual yield/TY)*100 = ?