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Wize University Chemistry Textbook > Stoichiometry

Percent Yield

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Percent Yield

So far we have been assuming that the reaction proceeds 100% to products. In reality, this is rarely the case!

When we are doing experiments in the lab we often lose some of our product by spilling it or residues of it get left on glassware and spatulas.



So far we have been calculating the theoretical yield.

Theoretical Yield - the maximum amount of product produced based on the quantity of the limiting reagent (e.g. the amount of product produced in a calculation).

Actual Yield - the actual amount of product produced in the reaction (e.g. the amount of product obtained in a laboratory experiment).


% yield= actual yieldtheoretical yield x100\boxed{\%\ yield=\ \frac{actual\ yield}{theoretical\ yield}\ x100}


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Test Your Understanding

1) In a lab, you measure your product and record 5.222g. This is the
actual
yield.

2) If everything went 100% perfectly according to the reaction we would get the
theoretical
yield

3) If I determined the limiting reagent, and then calculated the number of moles of product and the mass of product based on this, I've just calculated the
theoretical
yield

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Example: What is the Percent Yield

When 49.00 g of a hydrocarbon fuel with formula C7H10O2\text{C}_7\text{H}_{10}\text{O}_2 is reacted with excess oxygen, a total of 21.56 g of water is collected. What was the percent yield of the reaction?

2
C7H10O2 +
17
O2 →
10
H2O +
14
CO2

actual yield=21.56g water

m = 49 g
MW=126 g/mol
n = m/MW
n = 49 g / 126 g/mol
n = 0.38889 moles

Now we need to convert that into theoretical moles of water:
0.38889 moles divided by 2 multiplied by 10 = 1.945 moles of water
MW(water) = 18 g/mol

Now we need to calculate theoretical mass:
n = m/MW
m = nM
m = 1.945 mol x 18 g/mol
m = 35.01 g of water (theoretical mass)

In the question it states we produced 21.56 g of water (actual mass).

Now we can solve for % yield:
% yield = actual yield/theoretical yield x 100
% yield = 21.56 g / 35.01 g x 100
% yield = 62%

Practice: Calculate Moles Given Percent Yield

If the yield for the following reaction is 45%, how many moles of KClO3 are needed to produce 1 mol of O2?

2KClO3(s) → 2KCl(s) + 3O2(g)

Practice: Limiting Reagent & Percent Yield

Iron oxidizes when exposed to oxygen to form iron oxide according to the following equation:
Fe + O2 ​→ Fe2​O3​

352g of pure iron is exposed to 12.0 mols of O2, and after a period of time 46.7 g of iron oxide (rust) is collected.
What is the limiting reagent in this reaction?
Extra Practice
Percent Yield
If the yield for the following reaction is 45%, how many moles of KClO3 are needed to produce 1 mol of O2?
2KClO3(s) → 2KCl(s) + 3O2(g)
Stoichiometry
Consider the following reaction:
2 Ca3(PO4)2 (s) + 10 C (s) + 6 SiO2 (s) → 6 CaSiO3 (s) + 10 CO (g) + P4 (l)
An initial reaction mixture contains 15.0 g Ca3(PO4)2, 10.0 g SiO2, and 4.00 g C. After the reaction, 2.17 g P4 is obtained. What is the percent yield for this experiment?
Chemical Reactions: Actual Yield
Consider the following reaction:
PCℓ3+Cℓ2→PCℓ5PC\ell_3 + C\ell_2 \to PC\ell_5
If the yield of the reaction is 76.5 %, what is the mass of PCl5 , in grams, obtained from the reaction of 27.0 g of PCl3 with excess Cl2? Give your answer to one decimal place; do not include units in your answer.
Stoichiometry: Percent yield
In the balanced reaction below, a student reacts 1.25g of copper with 5.0mL of 12.0mol/L HCl.
Cu(s)+2HCℓ(aq)→CuCℓ2(aq)+H2(g)Cu(s)+ 2HC \ell(aq)\to CuC\ell_2(aq) +H_2(g)
Stoichiometry: Limiting Reagents
Vanillin acetate is a synthetic flavoring agent used to mimic the natural flavor of vanilla in candies, beverages, ice creams, and baked goods. You only need 10-30 ppm concentrations of vanillin acetate to flavor most foods! The preparation of this compound is described by the balanced reaction scheme below. Use the data provided to answer the following questions.
Chemical reactions: Limiting Reagent & Percent Yield
Iron oxidizes when exposed to oxygen to form iron oxide according to the following equation:
Fe (s) + O2 (g) ​→ Fe2​O3​ (s)
352g of pure iron is exposed to 12.0 mols of O2, and after a period of time, 46.7 g of iron oxide (rust) is collected.
Stoichiometry 2
An unknown hydrocarbon contains 40.0% C and 6.66% H by weight.
a. What is the empirical formula of the compound?
b. What is the molecular formula if molecular weight of the compound is 180 gmol-1?
Stoichiometry
Consider the following reaction:
2 Ca3(PO4)2 (s) + 10 C (s) + 6 SiO2 (s) → 6 CaSiO3 (s) + 10 CO (g) + P4 (l)
An initial reaction mixture contains 15.0 g Ca3(PO4)2, 10.0 g SiO2, and 4.00 g C. After the reaction, 2.17 g P4 is obtained. What is the percent yield for this experiment?
Consider the two following reactions:
CS2 + 3Cl2 → CCl4 (l)+ S2Cl2 (l) 60% yield
3 CCl4 (l) + 2 SbF3 (s) → 3 CCl2F2 (g) + 2SbCl3 (s) 80% yield
Consider the following reaction:
PCl3 + Cl2 = PCl5
If the yield of the reaction is 76.5 %, what is the amount of PCl5 obtained from 27.0 g of PCl3?
Precipitation
Zinc reacts with silver nitrate according to the following equation:
Zn (s) + 2AgNO3 (aq) → Zn(NO3)2 (aq) + 2Ag (s)
The concentration of AgNO3 solution is 1.330 molsL-1. 100 g Zn was added to 1.000 L of this solution and 90.0 g Ag is collected. What is the percent yield of this reaction?
Precipitation
CaSO4 can be converted to CaO at high temperature by the following two step procedure:
CaSO4 (s) + 4C → CaS (l) + 4CO (g)
CaS (l) + 3CaSO4 (s) → 4CaO (s) + 4SO2
Percent Yield
Sodium carbonate is an inexpensive compound that has a variety of applications. It is used in glass and paper manufacturing as well as in common foods like ramen noodles. The production of sodium carbonate occurs in a two step reaction as shown below:
1. H2O + NaCl + NH3 + CO2 → NH4Cl + NaHCO3
2. 2NaHCO3 → Na2CO3 + CO2 + H2O
Percent Yield
If the yield for the following reaction is 45%, how many moles of KClO3 are needed to produce 1 mol of O2?
2KClO3(s) → 2KCl(s) + 3O2(g)
CHEM 1011 (Dalhousie) - Stoichiometry
2. In the unbalanced reaction below, a student reacts 1.25 g of copper with 5.0 mL of 12.0 M HCl.
Cu (s)    +    HCl (aq)    →    CuCl2 (aq)    +    H2 (g)Cu\ \left(s\right)\ \ \ \ +\ \ \ \ HCl\ \left(aq\right)\ \ \ \ \rightarrow\ \ \ \ CuCl_2\ \left(aq\right)\ \ \ \ +\ \ \ \ H_2\ \left(g\right)
a) Calculate the theoretical yield of hydrogen gas produced in grams.
Stoichiometry: Limiting reagents
3. Consider the chemical reaction described below:
Ca3(PO4)2 (s)    +    C (s)    +    SiO2 (s)    →    CaSiO3 (s)    +    CO (g)    +    P (l)Ca_3\left(PO_4\right)_2\ \left(s\right)\ \ \ \ +\ \ \ \ C\ \left(s\right)\ \ \ \ +\ \ \ \ SiO_2\ \left(s\right)\ \ \ \ \rightarrow\ \ \ \ CaSiO_3\ \left(s\right)\ \ \ \ +\ \ \ \ CO\ \left(g\right)\ \ \ \ +\ \ \ \ P\ \left(l\right)
a) What is the limiting reagent for this reaction if an initial reaction mixture contains 1325 kg of calcium phosphate, 300 kg of carbon and 890 kg of silicon dioxide.
Chemical Reactions: Limiting Reagent
Based on the unbalanced chemical reaction below:
NaNO2 (s)    +    O2 (g)    →    NaNO3 (s)NaNO_2\ \left(s\right)\ \ \ \ +\ \ \ \ O_2\ \left(g\right)\ \ \ \ \rightarrow\ \ \ \ NaNO_3\ \left(s\right)
a) Calculate the mass of sodium nitrate if 10.25 g of sodium nitrite is reacted with 7.55 g of oxygen gas.
Chemical Reactions: Limiting Reagent & Percent Yield Practice
Iron oxidizes when exposed to oxygen to form iron oxide according to the following equation:
Fe + O2 ​→Fe2​O3​
352g of pure iron is exposed to 12.0 mols of O2, and after a period of time 46.7 g of iron oxide (rust) is collected.
Chemical Reactions: Percent Yield
If the yield for the following reaction is 45%, how many moles of KClO3 are needed to produce 1 mol of O2?
2KClO3(s) -> 2KCl(s) + 3O2(g)
Stoichiometry: Mass Percentage
How many grams of PCl3 are needed to produce 10g of POCl3 using an excess of hydrogen peroxide assuming a typical reaction yield of 78%?
PCl3+H2O2→POCl3+H2OPCl_3+H_2O_2\rightarrow POCl_3+H_2O
Stoichiometry: Percent yield
Consider the following unbalanced reaction:
C4H8O2+O2→CO2+H2O\rm C_4H_8O_2 +O_2 \to CO_2 + H_2O
If 36.00 g of C4H8O2\rm C_4H_8O_2 is burned, what mass of water would be collected if the reaction yield was 76%?
Stoichiometry: Percent Yield
A compound with the formula C7H8O3\text{C}_7\text{H}_8\text{O}_3 is burned to completion in excess O2\text{O}_2. If 18.0g of the organic compound was consumed in the reaction, how many grams of H2O\text{H}_2\text{O} will be collected if the yield was 85%?
The potassium salt of benzoic acid, potassium benzoate (KC7H5O2, MM=160 g/mol) can be made by the action of potassium permanganate on toluene (C7H8, MM=92 g/mol). If the yield of potassium benzoate cannot realistically be expected to be more than 71%, what is the minimum number of grams of toluene needed to produce 11.5 g of potassium benzoate?
C7H8+2KMnO4→KC7H5O2+2MnO2+KOH+H2OC_7 H_8+2KMnO_4→KC_7 H_5 O_2+2MnO_2+KOH+H_2 O
Stoichiometry: Percent Yield
How many grams of PCl3 are needed to produce 10g of OPCl3 using an excess of hydrogen peroxide assuming a typical reaction yield of 78%?
PCl3​ + H2​O2 ​→ OPCl3​ + H2​O
Chemical Reactions: Limiting Reagent & Percent Yield Practice
Iron oxidizes when exposed to oxygen to form iron oxide according to the following equation:
Fe + O2 ​→Fe2​O3​
352g of pure iron is exposed to 12.0 mols of O2, and after a period of time 46.7 g of iron oxide (rust) is collected.
Percent Yield
If the yield for the following reaction is 45%, how many moles of KClO3 are needed to produce 1 mol of O2?
2KClO3(s) -> 2KCl(s) + 3O2(g)
Aspirin is produced by the reaction of salicylic acid, C7H6O3\rm C_7H_6O_3, and acetic anhydride, C4H6O3\rm C_4H_6O_3
C7H6O3(s)+C4H6O3(l)→C9H8O4(s)+C2H4O2(l)\rm C_7H_6O_3(s)+C_4H_6O_3(l)\rightarrow C_9H_8O_4(s)+C_2H_4O_2(l)
If 2.04 g of C9H8O4\rm C_9H_8O_4 is produced from the reaction of 3.03 g C7H6O3\rm C_7H_6O_3 and 4.01 g C4H6O3\rm C_4H_6O_3, what is the percent yield?