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How do I calculate the "expected yield" for a reaction?
- I need to calculate % yield for my lab experiment. I know it equals actual yield/expected yield x100, but how do I calculate the expected yield? The equation is (CH3)3CNH2 + HC2H3O2 [(CH3)3CNH3]C2H3O2.
The expected or theoretical yield is the amount of product obtained if the limiting reagent reacts completely.
- Write the balanced equation for the reaction. You've already done that.
(For more about balancing equations, see How can I tell if an equation is balanced properly? and Ten tips for balancing equations).
- Identify the limiting reagent. In this case, every mole of (CH3)3CNH2 needs a mole of HC2H3O2, so whichever reactant is present in
the smaller molar amount will limit the amount of product obtained.
With more complex reactions, you can identify the limiting reagent by calculating the amount of product produced if each reactant in turn is consumed completely. (For an example, see How can amount of product be predicted when the amounts of two reactants are known?)
- Predict the amount of product obtained if the limiting reagent is consumed completely.
For example, if 0.100 mol of the amine (CH3)3CNH2 reacted with excess acetic acid
HC2H3O2, the expected yield of the product [(CH3)3CNH3]C2H3O2 is
0.100 mol amine
||(||1 mole product|
1 mol amine
||(||133 g product|
1 mole product
= 13.3 g product
Author: Fred Senese email@example.com