Question

If 45.0g of Li react with 20.0g N2 according to the equation below, find (A) how many grams of Li3N can be produced and (B) the percent yield if 35.0 g of Li3N were actually obtained.
6Li + N2 --> 2Li3N

Answer 1

1) calculate the limiting reactant

45.0g Li x 2/ (6 x MM Li )= X moles of Li3N

20.0g N2 x 2/ MM N2 = Y moles of Li3N

X<Y => Li is the limiting reactant
X<Y => N2 is the limiting reactant

2) to calculate A) multiply the moles of Li3N produced by the limiting reactant by the MM of Li3N

3) to calculate B) divide (35.0 g of Li3N x 100) by the grams of Li3N produced by the limiting reactant calculated in the step 2