Percent Yield and Limited Reactions

9.5 Percent Yield

Percent Yield

• In most reactions, some product is lost due to incomplete reactions or side reactions.

• Theoretical yield is the amount of product that you SHOULD get (it's calculated).

• Actual yield is the amount that you actually obtained, as the name implies.

If we can theoretically produce 43.1 grams of NH₃ in a reaction, but the actual yield is 26.0 grams of NH₃, what is the % yield?

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​Example:

• H₂S is the limiting reactant (because sufficient oxygen is present).

• 45.5 g SO₂ is the actual yield.

• We still need the theoretical yield (we have to calculate this).

Let's identify the #'s:

If 60.0 g of H₂S reacts with sufficient oxygen and produces 45.5 g of SO₂, what is the percent yield of SO₂?

2H₂S(g) + 3O₂(g) --> 2SO₂(g) + 2H₂O(g)

Fill in the Blanks

2H₂S(g) + 3O₂(g) --> 2SO₂(g) + 2H₂O(g)

If 60.0 g of H₂S reacts, how many grams of SO₂ SHOULD form? This is the theoretical yield.

When 60.0 g of H₂S reacts, you SHOULD produce 113 grams of SO₂.

This is the theoretical yield. This is what you would obtain in a perfect world.

theoretical yield:

If 60.0 g of H₂S reacts with sufficient oxygen and produces 45.5 g of SO₂, what is the percent yield of SO₂?

2H₂S(g) + 3O₂(g) --> 2SO₂(g) + 2H₂O(g)

Fill in the Blanks

When 60.0 g of H₂S reacts with sufficient oxygen and produces 45.5 g of SO₂, what is the percent yield? Remember, we calculated the theoretical yield to be 113 g.

Fill in the Blanks

2H₂S(g) + 3O₂(g) --> 2SO₂(g) + 2H₂O(g)

If 25.0 g of O₂ reacting with sufficient H₂S produces 18.6 g of SO₂, what is the percent yield of SO₂?

Fill in the Blanks

Valine, C₅H₁₁NO₂, an amino acid, reacts in the body according to the following reaction:

2C₅H₁₁NO₂(aq) + 12O₂(g) --> 9CO₂(g) + H₂O(l) + CH₄N₂O(aq)

How many grams of O₂ will react with 15.0 g of valine?

Fill in the Blanks

2C₅H₁₁NO₂(aq) + 12O₂(g) --> 9CO₂(g) + H₂O(l) + CH₄N₂O(aq)

How many grams of CO₂ are formed when 100. g of valine and 200. g of O₂ react?

Fill in the Blanks

2C₅H₁₁NO₂(aq) + 12O₂(g) --> 9CO₂(g) + H₂O(l) + CH₄N₂O(aq)

If 45.0 g of valine reacts to give 6.75 g of urea, what is the percent yield of urea?