C. Johannesson B. Percent Yield calculated on paper measured in lab.

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C. Johannesson B. Percent Yield calculated on paper measured in lab

C. Johannesson B. Percent Yield b Theoretical yield Is the calculated amount of product (what we get by solving stoichiometry problems) That’s how much you would get if you don’t make any mistakes and every molecule does exactly what you hoped.

C. Johannesson B. Percent Yield b Actual yield Is how much product you actually end up with in real life. It is always less than or equal to the theoretical yield. Because the law of conservation of matter means you can’t create extra atoms out of thin air. Lots of things can lead to a lower actual yield…

C. Johannesson B. Percent Yield b Actual yield is affected by things like: Spilling some reactant or product Overflowing the reaction vessel Burning product Lots of other lab errors ALSO: some reactions won’t go “to completion” no matter how careful you are. Some molecules are stubborn and refuse to react or do the wrong reaction.

C. Johannesson B. Percent Yield b When 45.8 g of K 2 CO 3 react with excess HCl, 46.3 g of KCl are formed. Calculate the theoretical and % yields of KCl. K 2 CO 3 + 2HCl  2KCl + H 2 O + CO g? g (actual: 46.3 g) We need to CALCULATE the theoretical yield. That’s going to be a regular 3-step stoich problem.

C. Johannesson B. Percent Yield 45.8 g K 2 CO 3 1 mol K 2 CO g K 2 CO 3 = 49.4 g KCl 2 mol KCl 1 mol K 2 CO g KCl 1 mol KCl K 2 CO 3 + 2HCl  2KCl + H 2 O + CO g? g (actual: 46.3 g) Theoretical Yield:

C. Johannesson B. Percent Yield Theoretical Yield = 49.4 g KCl % Yield = 46.3 g 49.4 g  100 = 93.7% K 2 CO 3 + 2HCl  2KCl + H 2 O + CO g49.4 g actual: 46.3 g

C. Johannesson B. Percent Yield Actual yield must be LESS than (or equal to) theoretical yield. Because percent yield must be LESS than (or equal to) 100% Theoretical Yield is the “total possible” That’s the most product the reaction can make If you start with 10 H atoms, you’ll never end up with more than 5 water molecules. Because each water molecule needs 2 hydrogens And once the H atoms are used up, that’s it.