Test your knowledge (for serious thinkers) Chem question dealing with theoretical yield..?

Question

Lithium and Nitrogen react to produce lithium nitride.

6Li(s) + N(subscipt 2)(g) yields 2 Li (subscipt 3)N(s)

If 3.50g of each reactant are used, the theoretical yield of lithium nitride is

A) 3.52g
B) 5.85g
C) 17.6g
D) 2.93g
E) 8.7g

Answers, not explanations, guys.

Answer 1

It is easy to first eliminate C and E. You are starting with maximum 7 grams. Your product cannot be more than 7 grams.
It cannot be less than 3.5 either, so that will eliminate D.

Just thinikng about it, Choice B seems to be the only reasonable conclusion, as 3.52 grams seems to be too small.

You can check by doing the actual stoichiometry. Convert the 3.5 grams of each reactant to moles and calculate the yield of Li3N based on the limiting reactant.

Answer 2

you have to look at the mass of a mole for each reactant to determine what % of the Li and N will actually react given the mole ration of 6 : 2 (Li : N)
Once you find the percentage yield,
multiply times 7 which is (3.5 * 2)g total mass