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General Chemistry Principles, Patterns, and Applications, 2011

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8. Calcium hydroxide <strong>and</strong> calcium carbonate are effective in neutralizing the effects of acid rain on lakes.<br />

Suggest other compounds that might be effective in treating lakes. Give a plausible reason to explain why<br />

Ca(OH) 2 <strong>and</strong> CaCO 3 are used.<br />

9. ♦ Approximately 95% of the chlorine produced industrially comes from the electrolysis of sodium chloride<br />

solutions (brine):<br />

NaCl(aq) + H 2 O(l) → Cl 2 (g) + H 2 (g) + NaOH(aq)<br />

Chlorine is a respiratory irritant whose presence is easily detected by its penetrating odor <strong>and</strong> greenishyellow<br />

color. One use for the chlorine produced is in the manufacture of hydrochloric acid.<br />

o. In the chemical equation shown, what has been oxidized <strong>and</strong> what has been reduced?<br />

p. Write the oxidation <strong>and</strong> reduction equations for this reaction.<br />

q. Balance the net ionic equation.<br />

r. Name another salt that might produce chlorine by electrolysis <strong>and</strong> give the expected products. Identify those<br />

products as gases, liquids, or solids.<br />

10. ♦ The lead/acid battery used in automobiles consists of six cells that produce a 12 V electrical system.<br />

During discharge, lead(IV) oxide, lead, <strong>and</strong> aqueous sulfuric acid react to form lead(II) sulfate <strong>and</strong> water.<br />

s. What has been oxidized <strong>and</strong> what has been reduced?<br />

t. Write <strong>and</strong> balance the equation for the reaction.<br />

u. What is the net ionic equation?<br />

v. What is the complete ionic equation?<br />

w. What hazard is associated with h<strong>and</strong>ling automobile batteries?<br />

11. ♦ The use of iron, which is abundant in Earth’s crust, goes back to prehistoric times. In fact, it is believed<br />

that the Egyptians used iron implements approximately 5000 years ago. One method for quantifying the iron<br />

concentration in a sample involves three steps. The first step is to dissolve a portion of the sample in<br />

concentrated hydrochloric acid to produce ferric chloride; the second is to reduce Fe 3+ to Fe 2+ using zinc metal;<br />

<strong>and</strong> the third is to titrate Fe 2+ with permanganate, producing Mn 2+ (aq) <strong>and</strong> ferric iron in the form of Fe 2 O 3 .<br />

x. Write chemical equations for all three steps.<br />

y. Write the net ionic equations for these three reactions.<br />

z. If 27.64 mL of a 1.032 M solution of permanganate are required to titrate 25.00 mL of Fe 2+ in the third step,<br />

how many grams of Fe were in the original sample?<br />

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

Saylor.org<br />

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