You react 2.0 g of O2 and collect 1.40 g of N2 gas. What is your percent yield?

Question

N2H4+O2–>N2+2H2O

partial answer: 7X.XX %

Answer 1

Percent yield is calculated as actual yield divided by theoretical yield (x100%). We are given the actual yield of 1.40 g, so we must first find the theoretical yield. This is exactly what has been done in your previous questions. We use the stoichiometry of the balanced equation and dimensional analysis.

N₂H₄ + O₂ ==> N₂ + 2H₂O ... balanced equation

Theoretical yield:

2.0 g O2 x 1 mol O2/32 g x 1 mol N2 / 1 mol O2 x 28 g N2/ mol N2 = 1.75 g N2

Percent yield:

1.40 g / 1.75 g (x100%) = 80.%

The answer you give of 7X.XX% can't be correct because 2.0 g has only 2 significant figures so you should'nt report your answer to 4 significant figures.