Chapter 3

A sample of a compound with the formula \(\mathrm{X}_{2} \mathrm{~S}_{3}\) has a mass of \(10.00 \mathrm{~g}\). It is then roasted (reacted with oxygen) to convert it to \(\mathrm{X}_{2} \mathrm{O}_{3}\). After roasting, it weighs \(7.410 \mathrm{~g}\). Calculate the atomic mass of \(\mathrm{X}\).

When solutions of silver nitrate and sodium carbonate are mixed, solid silver carbonate is formed and sodium nitrate remains in solution. If a solution containing \(12.43 \mathrm{~g}\) sodium carbonate is mixed with a solution containing \(8.37 \mathrm{~g}\) silver nitrate, calculate the mass of each of the four substances present after the reaction is complete.

Nickel metal reacts with aqueous silver nitrate in a displacement reaction to produce silver metal and aqueous nickel nitrate. Consider an experiment in which the reaction starts with \(12.0 \mathrm{~g}\) nickel metal and stops before all the nickel reacts. A total of \(24.0 \mathrm{~g}\) metal is present when the reaction stops. Calculate how many grams of each metal are present in the 24.0 -g mixture of metals.

Dolomite, found in soil, is \(\mathrm{CaMg}\left(\mathrm{CO}_{3}\right)_{2}\). If a \(20.0-\mathrm{g}\) sample of soil is titrated with \(65.25 \mathrm{~mL}\) of \(0.2500-\mathrm{M} \mathrm{HCl}\) calculate the mass percent of dolomite in the soil sample.

A \(60.0-\mathrm{mL}\) sample of \(2.00-\mathrm{M} \mathrm{NaCl}\) and a \(40.0-\mathrm{mL}\) sample of \(0.500-\mathrm{M} \mathrm{NaCl}\) are mixed. Then, additional distilled water is added until the total volume is \(500 . \mathrm{mL}\). Calculate the molarity of the \(\mathrm{NaCl}\) in the final solution.

Chlorine has several oxidation states. (a) Determine the oxidation state of chlorine in \(\mathrm{Cl}_{2}, \mathrm{HOCl}, \mathrm{ClO}_{2}, \mathrm{NH}_{4} \mathrm{Cl},\) and \(\mathrm{NaCl}\). (b) Chloride ion is the most stable form. Predict which of the other substances given in part (a) is an oxidizing or a reducing agent and rank them in decreasing order of their oxidizing strengths.

In the laboratory, you are given four unlabeled bottles. Each bottle contains a different aqueous solution: \(\mathrm{HCl}\), \(\mathrm{AgNO}_{3}, \mathrm{Na}_{2} \mathrm{CO}_{3},\) or \(\mathrm{NaOH}\). Devise an experimental procedure to identify the solute in each of the four bottles using only the aqueous solutions provided in the four bottles.

A mountain lake that is \(4.0 \mathrm{~km} \times 6.0 \mathrm{~km}\) with an average depth of \(75 \mathrm{~m}\) has an \(\mathrm{H}^{+}(\mathrm{aq})\) concentration of \(1.3 \times 10^{-6} \mathrm{M}\). Calculate the mass of calcium carbonate that would have to be added to the lake to change the \(\mathrm{H}^{+}\) (aq) concentration to \(6.3 \times 10^{-8} \mathrm{M}\). Assume that all the carbonate is converted to carbon dioxide, which bubbles out of the solution.

A 7.290 -mg mixture containing only cyclohexane and acetaldehyde, \(\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O},\) is analyzed by combustion analysis, which yielded \(21.999 \mathrm{mg} \mathrm{CO}_{2}\). Calculate the mass percent of acetaldehyde in the mixture.

Arsenic is often present in polluted water as sodium dihydrogen arsenate. It can be removed from water by reaction with iron(III) chloride, which precipitates iron(III) arsenate. (a) Write the balanced chemical equation for this reaction. (b) Write the net ionic equation. (c) Calculate the minimum volume of \(0.150-\mathrm{M}\) iron(III) chloride required to precipitate all of the arsenate from \(25.0 \mathrm{~mL}\) of a solution that contains \(0.025-\mathrm{M}\) arsenate. (d) Calculate the mass of iron(III) arsenate that precipitates.

The mass percent of ammonia in a commercial window cleaner was determined by titration with HCl. A \(9.360-\mathrm{g}\) sample of the window cleaner was diluted with \(35.778 \mathrm{~g}\) water and \(4.188 \mathrm{~g}\) of this diluted solution was titrated using \(13.58 \mathrm{~mL}\) of \(0.1093-\mathrm{M} \mathrm{HCl}\) to reach the equivalence point. Calculate the mass percent of ammonia in the window cleaner.

A commercial antacid tablet contains \(\mathrm{NaAl}(\mathrm{OH})_{2} \mathrm{CO}_{3}\) plus inert materials. A \(0.500-\mathrm{g}\) tablet is titrated and requires \(27.60 \mathrm{~mL}\) of \(0.425-\mathrm{M} \mathrm{HCl}\) to reach the equivalence point. Calculate the mass percent of \(\mathrm{NaAl}(\mathrm{OH})_{2} \mathrm{CO}_{3}\) in the tablet.

Ethanol, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH},\) is a gasoline additive that can be produced by fermentation of glucose. $$\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} \longrightarrow 2 \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}+2 \mathrm{CO}_{2}$$ (a) Calculate the mass (g) of ethanol produced by the fermentation of 1.000 lb glucose. (b) Gasohol is a mixture of \(10.00 \mathrm{~mL}\) ethanol per \(90.00 \mathrm{~mL}\) gasoline. Calculate the mass (in g) of glucose required to produce the ethanol in 1.00 gal gasohol. Density of ethanol \(=0.785 \mathrm{~g} / \mathrm{mL}\) (c) By 2022, the U. S. Energy Independence and Security Act calls for annual production of \(3.6 \times 10^{10}\) gal of ethanol, no more than \(40 \%\) of it produced by fermentation of corn. Fermentation of 1 ton \(\left(2.2 \times 10^{3} \mathrm{lb}\right)\) of corn yields approximately 106 gal of ethanol. The average corn yield in the United States is about \(2.1 \times 10^{5} \mathrm{lb}\) per \(1.0 \times 10^{5} \mathrm{~m}^{2} .\) Calculate the acreage (in \(\mathrm{m}^{2}\) ) required to raise corn solely for ethanol production in 2022 in the United States.

Dicobalt octacarbonyl, \(\mathrm{Co}_{2}(\mathrm{CO})_{8},\) is formed by the reaction of cobalt metal with carbon monoxide gas. (a) Calculate the maximum mass of dicobalt octacarbonyl that can be formed from \(100.0 \mathrm{~g}\) cobalt and \(200.0 \mathrm{~g}\) carbon monoxide, assuming \(89.7 \%\) yield. (b) Assuming that the deviation from \(100 \%\) yield was entirely due to loss of product during purification, calculate the additional mass of the limiting reactant that would be needed to react completely with the residual excess reactant. (c) Calculate the total mass of dicobalt octacarbonyl produced in the reactions in parts (a) and (b).