Calculating % Yield of NaN3 Experiment

[crybllrd]

Homework Statement

Use the unbalanced equation NaN₃ → Na + N₂ to answer the following question(s).
The % yield of an experiment in which two moles NaN₃ was used and 21 g nitrogen was isolated is ________.

Homework Equations

percent yield=({actual yield}/{theoretical yield})100%

The Attempt at a Solution

First, I balanced:

2NaN₃ → 2Na + 3N₂

And I convert my known mass to moles:

21g of N_{2}* \frac{3 mol N_{2}}{28 g N_{2}}=2.25 mol N_{2}

...and that's where I'm stuck. I'm preparing for a comprehensive final exam, and it seems I have forgotten this piece from the beginning of the semester.

Edit:The LATEX ref is failing for some reason. it is 21g(3mol/28g)=2.25 mol

 

[Borek]

LaTeX is OK, you were probably seeing cached image. That is a known problem.

What should be mass of nitrogen produced from 2 moles of NaN₃?

 

[p21bass]

Not to step on Borek's toes, or anything... And maybe I forgot something, but 21g(N₂) does not equal 2.25mol(N₂). There are 28.02g in one mol of nitrogen gas. Three mols N₂ = 42.03g. N=14.01g/mol.

 

[Borek]

You are right. I have ignored it completely as it is irrelevant to the question, my fault.