J.R. S. answered • 06/08/21
Ph.D. University Professor with 10+ years Tutoring Experience
So, Emma...you have posted several questions related to percent yield. I will demonstrate how to go about solving this problem, and hopefully you'll be able to do the others in the same or similar fashion.
Percent yield is defined as the actual yield divided by the theoretical yield (x100%). So, in order to calculate % yield, you must know or calculate theoretical yield, and you must know the actual yield. In this problem, the actual yield is given as 10.07 grams of SO2. We therefore must find (calculate) the theoretical yield.
Theoretical yield is the grams of SO2 that would be obtained if the reaction goes to completion and everything is perfect. That would be 100%. We calculate this from the mol ratios of the balanced equation and the amount of reactants used. From the balanced equation we see that ONE MOLE of C2H5NSCl produces ONE MOLE of SO2 (the mole ratio is 1:1). In this problem, we aren't given the amount of O2 used so we assume it is in excess. If you are given the amounts of other reactants, you must first find the limiting reactant (this is a topic for another post).
How many moles of C2H5NSCl do we have? The molar mass of this compound is 110.6 g/mol
37.5 g x 1 mol / 110.6 g = 0.339 moles C2H5NSCl
How many moles of SO2 can be expected (theoretically)?
0.339 mols C2H5NSCl x 1 mol SO2 / 1 mol C2H5NSCl = 0.339 mols SO2 theoretical yield
How many grams of SO2 is this?
molar mass SO2 = 64 g/mol
0.339 mols SO2 x 64 g / mol = 21.7 g SO2 theoretical yield
% yield = actual yield / theoretical yield (x100%) = 10.7 g / 21.7 g (x100%) = 49.3% yield
