You reacted 83.17 g of K with S to produce K2S. At the end of the experiment, you have 91.34 g of K2S. What is your theoretical and percent yields? 2 K + S → K2S

Answer 1

Hello, Kadie,

The balanced equation tells us that we should expect 1 mole of K₂S for every 1 mole S. That's a molar ratio of 1/2. Let's calculate the moles of S going in: 83.17 grams/(39.1 grams/mole) = 2.127 moles S. Therefore, we woud hope to find half that number of moles of K₂S. That would be 1.064 moles K₂S.

1.064 moles K₂S times the molar mass of K₂S will give us grams. A 100 percent yield would produce (1.064 moles)*(110.3 grams/mole) = 117.3 grams K₂S.

We got 91.3 grams. That is a yield of (91.34g/117.3g) = 77.89%

Bob