Percentage Yield

Phosphorous reacts with bromine to form phosphorous tribromide. If 35.0 grams of bromine are reacted and 27.9 grams of phosphorous tribromide are formed, what is the percent yield?

Answer explanation

1.Balanced equation:  2P + 3Br2  -->  2PBr3

2.Moles of reactant: n = m/M = (35 g)/(160g mol-1)  = 0.21875 mol

3.Molar ratio is 3:2, so 0.21875 : 0.1458 mol PBr3

4.Mr of product: PBr3 = (31*1) + (80*3) = 271 g mol-1

5.Theoretical yield: 0.1458 mol * 271 g mol-1 = 39.52 g

6.Percentage yield = (actual yield)/(theoretical yield)  x 100  =  (27.9 g)/(39.5 g)  x 100 = 70.6%

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Silver Nitrate reacts with Magnesium Chloride to produce Silver Chloride and Magnesium Nitrate. If 305 grams of silver nitrate are reacted in an excess of magnesium chloride producing 23.7 grams of magnesium nitrate, what is the percent yield?

Give your answer to 2 d.p.

Answer explanation

1.Balanced equation:  2AgNO3 + MgCl2  à  2AgCl + Mg(NO3)2

2.Moles of reactant: n = m/M = (305 g)/(170" " g mol-1)  = 1.79 mol

3.Molar ratio is 2:1, so 1.79 : 0.895 mol Mg(NO3)2

4.Mr of product: Mg(NO3)2 = (24*1) + (14*2) + (16*3*2) = 148 g mol-1

5.Theoretical yield: 0.895 mol * 148 g mol-1 = 132.46 g

6.Percentage yield = (actual yield)/(theoretical yield)  x 100  =  (23.7 g)/(132.46 g)  x 100 = 17.89 = 17.9%

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Zinc is reacted with Hydrochloric acid to form zinc chloride and hydrogen gas. The reaction is carried out in a glass container that has a mass of 14.7 grams. After placing the zinc in the glass container, the mass is 29.5 grams.

The hydrochloric acid is poured into the container and the zinc chloride is formed. The excess hydrochloric acid is removed leaving the glass container and the zinc chloride, which together have a mass of 37.5 grams. What is the percent yield?

Give your answer to 2 d.p.

Answer explanation

Be + 2HCl --> BeCl₂ + H₂

The theoretical yield of beryllium chloride was 10.7 grams. If the reaction actually yields 4.5 grams, what was the percent yield?

Answer explanation

A scientist began a reaction with 20 grams of lithium hydroxide and an excess amount of KCl. What is the theoretical yield of lithium chloride (grams)?

Answer explanation

A scientist began a reaction with 20 grams of lithium hydroxide and an excess amount of HCl. If the reaction produced 6 grams of lithium chloride what is the percentage yield?

Answer explanation

Nitrogen and hydrogen at high temperatures are converted to ammonia in a reaction known as the Haber process. When 400 grams of H₂ are added to an excess amount of N₂, 104 grams of NH₃ are formed. Calculate the percent yield.

Answer explanation

1) Write the balanced chemical equation, hydrogen and ammonia in a 3:2 ratio.

2) Calculate theoretical yield.

3) Calculate percentage yield.

Answer explanation

If the typical yield is 86.78%, how much SO₂ should be expected if 4897 grams of ZnS are used?

Answer explanation

When 5.00 g of KClO₃ is heated it decomposes according to the equation:

2KClO₃ → 2KCl + 3O₂

Give the % yield to 1 d.p. if 1.78 g of O₂ is produced.

Answer explanation