How do you calculate percent yield when there is no chemical equation?

Question

I did some research and found that you need a chemical equation to calculate percent yield, right? Problem is - I haven't been given one.

I'm in AP Chemistry and we're doing this lab on the purification of an impure substance. I have never taken Chemistry before so I'm clueless about everything.

In the lab instructions it just says "Create a data table to record all of the information necessary for you to calculate the percentage yield of benzoic acid"

What on earth is percent yield? Please use normal human language if you want to attempt to explain to me. Try using 5-year-old english if that's possible. Thanks.

Answer 1

% yield = (mass recovered) / (mass started with) x 100%

since your doing a purification if an impure substance you may be asked to calculate a % purity also...

% purity = (mass benzoic acid) / (mass impure substance) x 100%

examples...

if you started with 90 g benzoic acid and dissolved that in a solvent, then recovered 60 grams of benzoic acid, then your % yield would be

60 / 90 x 100% = 67% yield

if you started with say 75 grams of an "impure" substance and recovered 70 grams of pure benzoic acid, then the % purity would be

70 g / 75 g x 100% = 93%  

Answer 2

because you are only doing a purification you don't need an equation.  if you started with say 10 grams of whatever and after the purification you got 5 grams then the yield is half, 50%.