Stoichiometry

[Pages:3]Worksheet # 13

Stoichiometry 1. A laboratory method of preparing O2 gas involves the decomposition of solid KClO3

according to the following unbalanced equation: KClO3(s) KCl(s) + O2(g) a) How many moles of O2 (g) can be produced by the decomposition of 32.8 g KClO3? b) How many grams of KClO3 must be decomposed to produce 50.0 g O2? c) How many grams of KCl are formed when 23.8 grams O2 are formed in the decomposition of KClO3?

2. Suppose 9.5 g of gaseous C2H2 reacts with excess O2 according to the reaction below. What is the mass of CO2 produced? C2H2(g) + O2(g) CO2(g) + H2O()

3. Chlorine gas is made in the laboratory by the reaction of gaseous hydrochloric acid with solid manganese(IV) oxide to produce aqueous manganese(II) chloride, water, and chlorine. If 13.7 g of manganese(IV) oxide reacts with excess hydrochloric acid, how much chlorine is formed?

4. Solid bismuth oxide can react with carbon to form bismuth metal and carbon monoxide. How many grams of bismuth oxide reacted if 60.7 grams of bismuth is formed?

5. Solid chromium(III) oxide can react with gaseous hydrogen sulfide to form solid chromium(III) sulfide and water. How many grams of chromium(III) oxide are required to form 83.4 g of chromium(III) sulfide?

6. Solid potassium nitrate decomposes on heating to form solid potassium oxide, nitrogen, and oxygen. How many grams of potassium nitrate must be heated to form 86.6 kg of oxygen?

7. Solid silver oxide decomposes at temperatures in excess of 300 ?C, yielding metallic silver and oxygen gas. A 3.13 g sample of impure silver oxide yields 0.187 g oxygen. If silver oxide is the only source of O2, what is the percent silver oxide by mass in the sample?

8. The mineral galena (lead(II) sulfide) can be roasted it in the presence of oxygen to form solid lead(II) oxide and sulfur dioxide. A 5.77 g sample of impure galena yields 2.11 g lead(II) oxide. If the galena is the only source of lead(II) oxide, what is the percent galena in the impure sample?

9. How many moles of CO2 are produced by the reaction of 6.0 mol of MgCO3?

MgCO3 = MgO + CO2

10. Suppose that 1.6 mol Al2(SO4)3 are produced. How many moles of H2O are also produced? 2Al(OH)3 + 3H2SO4 = Al2(SO4)3 + 6H2O

11. According to reaction equation below, how many moles of H2C2O4 react completely with 1.5 mol of KMnO4? 2KMnO4 + 5H2C2O4 + 6HCl = 2MnCl2 + 10 CO2 + 2KCl + 8H2O

Worksheet 13

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12. When 0.45 mol of CO2 are produced by the reaction above, how many grams of H2O are also produced?

13. How many grams of H2SO4 are required for the complete reaction of 65.0 g of Al(OH)3? 2Al(OH)3 + 3H2SO4 = Al2(SO4)3 + 6H2O

14. How many grams of HCl are required for the complete reaction of 316 g KMnO4? 2KMnO4 + 5H2C2O4 + 6HCl = 2MnCl2 + 10CO2 + 2KCl + 8H2O

Answers to Worksheet #13 Stoichiometry The first step to stoichiometry is to write and balance the equation. If an equation is given to you, always check to make sure that it is balanced! Once the equation is balanced, use the stoichiometric coefficients and dimensional analysis to go from what you know everything about to what you want to know.

1. 2 KClO3(s) 2 KCl(s) + 3 O2(g)

a)

molO2

=

32.8gKClO3

1molKClO3 122.55g

3molO2 2molKClO3

= 0.401molO2

b) mass(g)KClO3 = 50.0gO2

1molO2 32.00g

2molKClO3 3molO2

122.55g 1molKClO3

= 128gKClO3

c)

mass( g ) KCl

=

23.8gO2

1molO2 32.00g

2molKCl 3molO2

74.55g 1molKCl

= 37.0gKCl

2. 2 C2H2(g) + 5 O2(g) 4 CO2(g) + 2 H2O()

mass( g )CO2

=

9.5 gC2 H 2

1molC2 H 2 26.036g

4molCO2 2molC2 H 2

44.01g 1molCO2

= 32gCO2

3. 4 HCl(g) + _ MnO2(s) _ MnCl2(aq) + 2 H2O() + _ Cl2(g)

mass( g )Cl2

= 13.7gMnO2

1molMnO2 86.94g

1molCl2 1molMnO2

70.90g 1molCl2

= 11.2gCl2

4. _ Bi2O3(s) + 3 C(s) 2 Bi(s) + 3 CO(g)

mass(g)Bi2O3 = 60.7gBi

1molBi 209.0g

1molBi2O3 2molBi

466.0g molBi2O3

= 67.7gBi2O3

5. _ Cr2O3(s) + 3 H2S(g) _ Cr2S3(s) + 3 H2O()

mass( g )Cr2O3

=

83.4 gCr2 S3

1molCr2S3 200.21g

1molCr2O3 1molCr2S3

152.00g 1molCr2O3

= 63.3gCr2O3

6. 4KNO3(s) 2K2O(s) + 2N2(g) + 5O2(g)

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mass(g)KNO3 = 86.6gO2

1molO2 32.00g

4molKNO3 5molO2

101.11g 1molKNO3

= 219gKNO3

7. 2 Ag2O(s) 4 Ag(s) + _ O2(g)

mass(g) Ag2O

=

0.187 gO2

1molO2 32.00g

2molAg2O 231.8g 1molO2 1molAg2O

= 2.71gAg2O

%

Ag2O

=

2.71g 3.13g

100

=

86.6%

8. 2PbS(s) + 3O2(g) 2PbO(s) + 2SO2(g) mass(g)PbS = 2.11gPbO 1molPbO 2molPbS 239.27g = 2.26gPbS 223.2g 2molPbO 1molPbS

%PbS

=

2.26g 5.77 g

100

=

39.2%

9.

6.0 mol CO2

? mol CO2

= 6.0 mol MgCO3

mol CO2 mol MgCO3

10. 9.6 mol H2O

? mol H2O = 1.6

mol Al2 (SO4 )3

6 mol H2O mol Al2 (SO4 )3

11. 3.8 mol H2C2O5

? mol H2C2O4

= 1.5

mol KMnO4

5 mol H2C2O5 2 mol KMnO4

12. 6.5 g H2O

? g H2O = 0.45 mol CO2

8 mol H2O 10 mol CO2

18.0 g H2O mol H2O

13. 122 g H2SO4

? g

H 2SO4

= 65.0

g

Al(OH)3

mol Al(OH)3 78.0 g Al(OH)3

3 mol H2SO4 2 mol Al(OH)3

98.1 g H2SO4 mol H2SO4

14. 219 g HCl

? g HCl = 316 g

K MnO4

mol K MnO4 158 g KMnO4

2

6 mol HCl mol KMnO4

36.5 g HCl mol HCl

Worksheet 13

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