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General Chemistry Principles, Patterns, and Applications, 2011

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11. ♦ Lead sulfide <strong>and</strong> hydrogen peroxide react to form lead sulfate <strong>and</strong> water. This reaction is used to clean oil<br />

paintings that have blackened due to the reaction of the lead-based paints with atmospheric hydrogen<br />

sulfide.<br />

a. Write the balanced chemical equation for the oxidation of lead sulfide by hydrogen peroxide.<br />

b. What mass of hydrogen peroxide would be needed to remove 3.4 g of lead sulfide?<br />

c. If the painting had originally been covered with 5.4 g of lead sulfide <strong>and</strong> you had 3.0 g of hydrogen peroxide,<br />

what percent of the lead sulfide could be removed?<br />

12. ♦ It has been suggested that diacetylene (C 4 H 2 , HC≡C–C≡CH) may be the ozone of the outer planets. As the<br />

largest hydrocarbon yet identified in planetary atmospheres, diacetylene shields planetary surfaces from<br />

ultraviolet radiation <strong>and</strong> is itself reactive when exposed to light. One reaction of diacetylene is an important<br />

route for the formation of higher hydrocarbons, as shown in the following chemical equations:<br />

C 4 H 2 (g) + C 4 H 2 (g) → C 8 H 3 (g) + H(g)C 8 H 3 (g) + C 4 H 2 (g) → C 10 H 3 (g) + C 2 H 2 (g)<br />

Consider the second reaction.<br />

a. Given 18.4 mol of C 8 H 3 <strong>and</strong> 1000 g of C 4 H 2 , which is the limiting reactant?<br />

b. Given 2.8 × 10 24 molecules of C 8 H 3 <strong>and</strong> 250 g of C 4 H 2 , which is the limiting reactant?<br />

c. Given 385 g of C 8 H 3 <strong>and</strong> 200 g of C 4 H 2 , which is in excess? How many grams of excess reactant would remain?<br />

d. Suggest why this reaction might be of interest to scientists.<br />

13. ♦ Glucose (C 6 H 12 O 6 ) can be converted to ethanol <strong>and</strong> carbon dioxide using certain enzymes. As alcohol<br />

concentrations are increased, however, catalytic activity is inhibited, <strong>and</strong> alcohol production ceases.<br />

a. Write a balanced chemical equation for the conversion of glucose to ethanol <strong>and</strong> carbon dioxide.<br />

b. Given 12.6 g of glucose, how many grams of ethanol would be produced, assuming complete conversion?<br />

c. If 4.3 g of ethanol had been produced, what would be the percent yield for this reaction?<br />

d. Is a heterogeneous catalyst or a homogeneous catalyst used in this reaction?<br />

e. You have been asked to find a way to increase the rate of this reaction given stoichiometric quantities of each<br />

reactant. How would you do this?<br />

14. Early spacecraft developed by the National Aeronautics <strong>and</strong> Space Administration for its manned missions<br />

used capsules that had a pure oxygen atmosphere. This practice was stopped when a spark from an electrical<br />

short in the wiring inside the capsule of the Apollo 1 spacecraft ignited its contents. The resulting explosion<br />

Saylor URL: http://www.saylor.org/books<br />

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