Percentage Yield and Percentage Purity



Chem 11 Name: _________________

Stoichiometry: Percentage Yield and Percentage Purity

1. Consider the reaction:

4Al(s) + 3O2(g) ( 2Al2O3(s)

(a) A 20.0 g sample of Al(s) reacts to produce 32.7 g of Al2O3(s). What is the percentage yield of the reaction? (1a) 86.5%

(b) If this reaction has a percentage yield of 74.2%, what mass of Al2O3(s) can be produced with 50.0 g of Al(s)? (1b) 70.1 g

(c) What mass of Al(s) is required to make 100.0 g of Al2O3(s) if the reaction has a percentage yield of 64.7%? (1c) 81.8 g

2. Consider the reaction:

4KO2(s) + 2CO2(g) ( 2K2CO3(s) + 3O2(g)

(a) A 30.0 g sample of KO2(s) is 59.3% pure. What mass of K2CO3(s) can the sample produce? (2a) 17.3 g

(b) Another sample of KO2(s) with a mass of 150.0 g is reacted so as to produce 89.7 g of K2CO3(s). What is the percentage purity of the KO2(s)? (2b) 61.5%

(c) A 15.0 g sample of pure KO2(s) produces 7.62 g of K2CO3(s). What is the percentage yield of the reaction? (2c) 52.3%

(d) What mass of KO2(g) with a purity of 64.8% is needed to make 100.0 g of K2CO3(s)? (2d) 158.8 g

3. A chemist wants to produce 50.0 g of NaCl by reacting sodium with chlorine gas according to the equation:

2Na + Cl2 ( 2NaCl

If this reaction has a percent yield of 77.3%, what mass of sodium must be reacted? (3) 25.4 g

4. The production of silver from the reaction

2AgNO3 + Cu ( Cu(NO3)2 + 2Ag

has a 74.2% yield. What mass of copper is required to obtain 100.0 g of silver? (4) 39.7 g

5. Consider the reaction:

Fe3O4 + 4H2 ( 3Fe + 4H2O

(a) A 35.0 g sample of Fe3O4 is 43.8% pure. What mass of Fe can the sample produce? (5a) 11.1 g

(b) Another sample of Fe3O4 with a mass of 126.7 g is reacted so as to produce 39.3 g of Fe. What is the percentage purity of Fe3O4? (5b) 42.9%

(c) A 20.0 g sample of pure Fe3O4 produces 5.98 g of Fe. What is the percentage yield of the reaction? (5c) 41.3%

(d) What mass of Fe3O4 with a purity of 59.4% is needed to make 50.0 g of Fe? (5d) 116.4 g

6. What mass of CuO is required to make 10.0 g of Cu according to the reaction

[pic]

if the reaction has a 58.0% yield

7. A student reacts 25.0 mL of benzene (C6H6, density = 0.879g/mL) with a “nitrating mixture” containing excess nitric acid to make 18.0 mL of nitrobenzene (C6H5NO2, density =1.204 g/mL) according to the equation

[pic]

a) What is the percentage yield of the reaction?

b) What mass of C6H6 is left unreacted?

8. The reaction [pic] produces 2.50 g of H2O when 12.20 g of SiO2 is treated with a small excess of HF.

a) What mass of SiF4 is formed?

b) What mass of SiO2 is left unreacted?

c) What is the percentage yield of the SiF44?

9. When 5.000 kg of malachite ore containing 4.30% of malachite, Cu2(OH)2CO3, is heated, the product is copper (II) oxide:

[pic]

a) If the reaction has an 84.0% yield, how many grams of CuO are produced?

b) If the decomposition reaction has an 87.0% yield, what mass of ore containing 3.70% malachite is required to produce 100.0g of CuO?

This side key: Answer Key:

Answer Key:

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