N2 + 2 O2 ---> 2 NO2.

Question

Suppose 31.25 g of N and 44.0 g of oxygen react.
A. Calculate the mass of Nitrogen dioxide formed.
B. Which reactant is the limiting reactant?
C. Calculate the mass of the excess reactant left after the reaction.
D. Find the % yield if 52.3 g of NO2 is produced

Answer 1

a & b.
mols N2 = grams/molar mass
mols O2 = grams/molar mass

Using the coefficients in the balanced equation convert mols N2 to mols NO2.
Do the same for mols O2 to mols NO2.\
It is likely that the mol values will be different which means one of them is not right. The correct value in limiting reagent (LR) problems is ALWAYS the smaller value and the reagent producing that value is the LR. The non-limiting reagent is the excess reagent (ER).
Using the smaller value convert that to grams. g = mol x molar mass. This is the theoretical yield(TY)

c.
Using the coefficients in the balanced equation, convert mols LR used (all of it of course) to mols used of ER. Then mols initially - mols used = mols left.

d.
%yield = (actual yield)/TY)*100 = ?