Chapter 4

Classify each of the following reactions as a combination reaction, decomposition reaction, displacement reaction, or combustion reaction. a. When solid calcium oxide, \(\mathrm{CaO}\), is exposed to gaseous sulfur trioxide, \(\mathrm{SO}_{3}\), solid calcium sulfate, \(\mathrm{CaSO}_{4}\), is formed. b. Calcium metal (solid) reacts with water to produce a solution of calcium hydroxide, \(\mathrm{Ca}(\mathrm{OH})_{2}\), and hydrogen gas. c. When solid sodium hydrogen sulfite, \(\mathrm{NaHSO}_{3}\), is heated, solid sodium sulfite, \(\mathrm{Na}_{2} \mathrm{SO}_{3}\), sulfur dioxide gas, \(\mathrm{SO}_{2}\), and water vapor are formed. d. Magnesium reacts with bromine to give magnesium bromide, \(\mathrm{MgBr}_{2}\).

Consider the reaction of all pairs of the following compounds in water solution: \(\mathrm{Sr}(\mathrm{OH})_{2}, \mathrm{AgNO}_{3}, \mathrm{H}_{3} \mathrm{PO}_{4}, \mathrm{KNO}_{3}\) \(\mathrm{CuSO}_{4}\) a. Which pair (or pairs) forms one insoluble compound and one soluble compound (not water)? b. Which pair (or pairs) forms two insoluble compounds? C. Which pair (or pairs) forms one insoluble compound and water?

An aqueous solution contains \(4.50 \mathrm{~g}\) of calcium chloride, \(\mathrm{CaCl}_{2}\), per liter. What is the molarity of \(\mathrm{CaCl}_{2}\) ? When calcium chloride dissolves in water, the calcium ions, \(\mathrm{Ca}^{2+}\), and chloride ions, \(\mathrm{Cl}^{-}\), in the crystal go into the solution. What is the molarity of each ion in the solution?

An aqueous solution contains \(3.45 \mathrm{~g}\) of iron(III) sulfate, \(\mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}\), per liter. What is the molarity of \(\mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}\) ? When the compound dissolves in water, the \(\mathrm{Fe}^{3+}\) ions and \(\mathrm{SO}_{4}{\underline{\phantom{xx}}}^{2-}\) ions in the crystal go into the solution. What is the molar concentration of each ion in the solution?

A stock solution of potassium dichromate, \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\), is made by dissolving \(89.3 \mathrm{~g}\) of the compound in \(1.00 \mathrm{~L}\) of solution. How many milliliters of this solution are required to prepare \(1.00 \mathrm{~L}\) of \(0.100 \mathrm{M} \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7} ?\)

A \(71.2-g\) sample of oxalic acid, \(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\), was dissolved in \(1.00 \mathrm{~L}\) of solution. How would you prepare \(1.00 \mathrm{~L}\) of \(0.150 \mathrm{M}\) \(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\) from this solution?

A solution contains \(6.00 \%\) (by mass) NaBr (sodium bromide). The density of the solution is \(1.046 \mathrm{~g} / \mathrm{cm}^{3}\). What is the molarity of \(\mathrm{NaBr}\) ?

An aqueous solution contains \(4.00 \% \mathrm{NH}_{3}\) (ammonia) by mass. The density of the aqueous ammonia is \(0.979 \mathrm{~g} / \mathrm{mL}\). What is the molarity of \(\mathrm{NH}_{3}\) in the solution?

A barium mineral was dissolved in hydrochloric acid to give a solution of barium ion. An excess of potassium sulfate was added to \(50.0 \mathrm{~mL}\) of the solution, and \(1.128 \mathrm{~g}\) of barium sulfate precipitate formed. Assume that the original solution was barium chloride. What was the molarity of \(\mathrm{BaCl}_{2}\) in this solution?

Bone was dissolved in hydrochloric acid, giving \(50.0 \mathrm{~mL}\) of solution containing calcium chloride, \(\mathrm{CaCl}_{2} .\) To precipitate the calcium ion from the resulting solution, an excess of potassium oxalate was added. The precipitate of calcium oxalate, \(\mathrm{CaC}_{2} \mathrm{O}_{4}\), weighed \(1.437 \mathrm{~g} .\) What was the molarity of \(\mathrm{CaCl}_{2}\) in the solution?

You have a sample of a rat poison whose active ingredient is thallium(I) sulfate. You analyze this sample for the mass percentage of active ingredient by adding potassium iodide to precipitate yellow thallium(I) iodide. If the sample of rat poison weighed \(759.0 \mathrm{mg}\) and you obtained \(212.2 \mathrm{mg}\) of the dry precipitate, what is the mass percentage of the thallium(I) sulfate in the rat poison?

An antacid tablet has calcium carbonate as the active ingredient; other ingredients include a starch binder. You dissolve the tablet in hydrochloric acid and filter off insoluble material. You add potassium oxalate to the filtrate (containing calcium ion) to precipitate calcium oxalate. If a tablet weighing \(0.680 \mathrm{~g}\) gave \(0.629 \mathrm{~g}\) of calcium oxalate, what is the mass percentage of active ingredient in the tablet?

A sample of \(\mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O}\) was heated to \(110^{\circ} \mathrm{C}\), where it lost water and gave another hydrate of copper(II) ion that contains \(32.50 \%\) Cu. A \(98.77\) -mg sample of this new hydrate gave \(116.66 \mathrm{mg}\) of barium sulfate precipitate when treated with a barium nitrate solution. What is the formula of the new hydrate?

A sample of \(\mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O}\) was heated to \(100^{\circ} \mathrm{C}\), where it lost water and gave another hydrate of copper(II) ion that contained \(29.76 \%\) Cu. An \(85.42-\mathrm{mg}\) sample of this new hydrate gave \(93.33 \mathrm{mg}\) of barium sulfate precipitate when treated with a barium nitrate solution. What is the formula of the new hydrate?

A water-soluble compound of gold and chlorine is treated with silver nitrate to convert the chlorine completely to silver chloride, \(\mathrm{AgCl}\). In an experiment, \(328 \mathrm{mg}\) of the compound gave \(464 \mathrm{mg}\) of silver chloride. Calculate the percentage of \(\mathrm{Cl}\) in the compound. What is its empirical formula? 4.122 A solution of scandium chloride was treated with silver nitrate. The chlorine in the scandium compound was converted to silver chloride, AgCl. A \(58.9\) -mg sample of scandium chloride gave \(167.4 \mathrm{mg}\) of silver chloride. What are the mass percentages of \(\mathrm{Sc}\) and \(\mathrm{Cl}\) in scandium chloride? What is its empirical formula?

A solution of scandium chloride was treated with silver nitrate. The chlorine in the scandium compound was converted to silver chloride, \(\mathrm{AgCl}\). A \(58.9\) -mg sample of scandium chloride gave \(167.4 \mathrm{mg}\) of silver chloride. What are the mass percentages of \(\mathrm{Sc}\) and \(\mathrm{Cl}\) in scandium chloride? What is its empirical formula?

A \(0.608-\mathrm{g}\) sample of fertilizer contained nitrogen as ammonium sulfate, \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}\). It was analyzed for nitrogen by heating with sodium hydroxide. \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}(s)+2 \mathrm{NaOH}(a q) \longrightarrow\) $$ \mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l)+2 \mathrm{NH}_{3}(g) $$ The ammonia was collected in \(46.3 \mathrm{~mL}\) of \(0.213 \mathrm{M} \mathrm{HCl}\) (hydrochloric acid), with which it reacted. $$ \mathrm{NH}_{3}(g)+\mathrm{HCl}(a q) \longrightarrow \mathrm{NH}_{4} \mathrm{Cl}(a q) $$ This solution was titrated for excess hydrochloric acid with \(44.3 \mathrm{~mL}\) of \(0.128 \mathrm{M} \mathrm{NaOH}\). $$ \mathrm{NaOH}(a q)+\mathrm{HCl}(a q) \longrightarrow \mathrm{NaCl}(a q)+\mathrm{H}_{2} \mathrm{O}(l) $$ What is the percentage of nitrogen in the fertilizer?

An antacid tablet contains sodium hydrogen carbonate, \(\mathrm{NaHCO}_{3}\), and inert ingredients. A \(0.500-\mathrm{g}\) sample of powdered tablet was mixed with \(50.0 \mathrm{~mL}\) of \(0.190 \mathrm{M} \mathrm{HCl}\) (hydrochloric acid). The mixture was allowed to stand until it reacted. $$ \mathrm{NaHCO}_{3}(s)+\mathrm{HCl}(a q) \longrightarrow \mathrm{NaCl}(a q)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{CO}_{2}(g) $$ The excess hydrochloric acid was titrated with \(47.1 \mathrm{~mL}\) of \(0.128\) \(M \mathrm{NaOH}\) (sodium hydroxide). $$ \mathrm{HCl}(a q)+\mathrm{NaOH}(a q) \longrightarrow \mathrm{NaCl}(a q)+\mathrm{H}_{2} \mathrm{O}(l) $$ What is the percentage of sodium hydrogen carbonate in the antacid?

If \(45.1 \mathrm{~mL}\) of a solution containing \(8.30 \mathrm{~g}\) of silver nitrate is added to \(30.6 \mathrm{~mL}\) of \(0.511 M\) sodium carbonate solution, calculate the molarity of silver ion in the resulting solution. (Assume volumes are additive.)

If \(38.2 \mathrm{~mL}\) of \(0.248 \mathrm{M}\) aluminum sulfate solution is diluted with deionized water to a total volume of \(0.639 \mathrm{~L}\), how many grams of aluminum ion are present in the diluted solution?

An aluminum nitrate solution is labeled \(0.256 \mathrm{M}\). If \(31.6\) \(\mathrm{mL}\) of this solution is diluted to a total of \(63.7 \mathrm{~mL}\), calculate the molarity of nitrate ion in the resulting solution.

Zinc acetate is sometimes prescribed by physicians for the treatment of Wilson's disease, which is a genetically caused condition wherein copper accumulates to toxic levels in the body. If you were to analyze a sample of zinc acetate and find that it contains \(3.33 \times 10^{23}\) acetate ions, how many grams of zinc acetate must be present in the sample?

Arsenic acid, \(\mathrm{H}_{3} \mathrm{~A} \mathrm{~s} \mathrm{O}_{4}\), is a poisonous acid that has been used in the treatment of wood to prevent insect damage. Arsenic acid has three acidic protons. Say you take a 26.14-mL sample of arsenic acid and prepare it for titration with \(\mathrm{NaOH}\) by adding \(25.00 \mathrm{~mL}\) of water. The complete neutralization of this solution requires the addition of \(53.07 \mathrm{~mL}\) of \(0.6441 \mathrm{M} \mathrm{NaOH}\) solution. Write the balanced chemical reaction for the titration, and calculate the molarity of the arsenic acid sample.

When the following equation is balanced by the halfreaction method using the smallest set of whole-number stoichiometric coefficients possible, how many electrons are canceled when the two half-reactions are added together? $$ \mathrm{K}(s)+\mathrm{N}_{2}(g) \Rightarrow \mathrm{K}_{3} \mathrm{~N}(s) $$

Identify each of the following reactions as being a neutralization, precipitation, or oxidation-reduction reaction. a. \(\mathrm{Fe}_{2} \mathrm{O}_{3}(s)+3 \mathrm{CO}(g) \longrightarrow 2 \mathrm{Fe}(s)+3 \mathrm{CO}_{2}(g)\) b. \(\mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+\mathrm{Hg}\left(\mathrm{NO}_{3}\right)_{2}(a q) \longrightarrow\) $$ \mathrm{HgSO}_{4}(s)+2 \mathrm{NaNO}_{3}(a q) $$ c. \(\mathrm{CsOH}(a q)+\mathrm{HClO}_{4}(a q) \longrightarrow\) $$ \mathrm{Cs}^{+}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{ClO}_{4}^{-}(a q) $$ d. \(\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}(g)+\mathrm{Na}_{2} \mathrm{~S}(a q) \longrightarrow \mathrm{MgS}(s)+2 \mathrm{NaNO}_{3}(a q)\)

A 414-mL sample of \(0.196 M \mathrm{MgBr}_{2}\) solution is prepared in a large flask. A \(43.0-\mathrm{mL}\) portion of the solution is then placed into an empty \(100.0-\mathrm{mL}\) beaker. What is the concentration of the solution in the beaker?

Three \(1.0-\mathrm{g}\) samples of \(\mathrm{PbCl}_{2}, \mathrm{KCl}\), and \(\mathrm{CaCl}_{2}\) are placed in separate \(500-\mathrm{mL}\) beakers. In each case, enough \(25^{\circ} \mathrm{C}\) water is added to bring the total volume of the mixture to \(250 \mathrm{~mL}\). Each of the mixtures is then stirred for five minutes. Which of the mixtures will have the highest concentration of chloride (Cl \(^{-}\) ) ion?

Lead(II) nitrate reacts with cesium sulfate in an aqueous precipitation reaction. What are the formulas of lead(II) nitrate and cesium sulfate? Write the molecular equation and net ionic equation for the reaction. What are the names of the products? Give the molecular equation for another reaction that produces the same precipitate.

Silver nitrate reacts with strontium chloride in an aqueous precipitation reaction. What are the formulas of silver nitrate and strontium chloride? Write the molecular equation and net ionic equation for the reaction. What are the names of the products? Give the molecular equation for another reaction that produces the same precipitate.

Elemental bromine is the source of bromine compounds. The element is produced from certain brine solutions that occur naturally. These brines are essentially solutions of calcium bromide that, when treated with chlorine gas, yield bromine in a displacement reaction. What are the molecular equation and net ionic equation for the reaction? A solution containing \(40.0 \mathrm{~g}\) of calcium bromide requires \(14.2 \mathrm{~g}\) of chlorine to react completely with it, and \(22.2 \mathrm{~g}\) of calcium chloride is produced in addition to whatever bromine is obtained. How many grams of calcium bromide are required to produce \(10.0\) pounds of bromine?

Barium carbonate is the source of barium compounds. It is produced in an aqueous precipitation reaction from barium sulfide and sodium carbonate. (Barium sulfide is a soluble compound obtained by heating the mineral barite, which is barium sulfate, with carbon.) What are the molecular equation and net ionic equation for the precipitation reaction? A solution containing \(33.9 \mathrm{~g}\) of barium sulfide requires \(21.2 \mathrm{~g}\) of sodium carbonate to react completely with it, and \(15.6 \mathrm{~g}\) of sodium sulfide is produced in addition to whatever barium carbonate is obtained. How many grams of barium sulfide are required to produce \(5.00\) tons of barium carbonate? (One ton equals 2000 pounds.)

Mercury(II) nitrate is treated with hydrogen sulfide, \(\mathrm{H}_{2} \mathrm{~S}\), forming a precipitate and a solution. Write the molecular equation and the net ionic equation for the reaction. An acid is formed; is it strong or weak? Name each of the products. If \(81.15 \mathrm{~g}\) of mercury(II) nitrate and \(8.52 \mathrm{~g}\) of hydrogen sulfide are mixed in \(550.0 \mathrm{~g}\) of water to form \(58.16 \mathrm{~g}\) of precipitate, what is the mass of the solution after the reaction?

Mercury(II) nitrate is treated with hydrogen sulfide, \(\mathrm{H}_{2} \mathrm{~S}\), forming a precipitate and a solution. Write the molecular equation and the net ionic equation for the reaction. An acid is formed; is it strong or weak? Name each of the products. If \(65.65 \mathrm{~g}\) of mercury(II) nitrate and \(4.26 \mathrm{~g}\) of hydrogen sulfide are mixed in \(395.0 \mathrm{~g}\) of water to form \(54.16 \mathrm{~g}\) of precipitate, what is the mass of the solution after the reaction?

Iron forms a sulfide with the approximate formula \(\mathrm{Fe}_{7} \mathrm{~S}_{8}\). Assume that the oxidation state of sulfur is \(-2\) and that iron atoms exist in both \(+2\) and \(+3\) oxidation states. What is the ratio of Fe(II) atoms to Fe(III) atoms in this compound?

A transition metal \(\mathrm{X}\) forms an oxide of formula \(\mathrm{X}_{2} \mathrm{O}_{3} .\) It is found that only \(50 \%\) of \(X\) atoms in this compound are in the \(+3\) oxidation state. The only other stable oxidation states of \(\mathrm{X}\) are \(+2\) and \(+5 .\) What percentage of \(X\) atoms are in the \(+2\) oxidation state in this compound?

What volume of a solution of ethanol, \(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}\), that is \(94.0 \%\) ethanol by mass contains \(0.200 \mathrm{~mol} \mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O} ?\) The density of the solution is \(0.807 \mathrm{~g} / \mathrm{mL}\).

What volume of a solution of ethylene glycol, \(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}_{2}\), that is \(56.0 \%\) ethylene glycol by mass contains \(0.350\) mol \(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}_{2}\) ? The density of the solution is \(1.072 \mathrm{~g} / \mathrm{mL}\).

A \(10.0-\mathrm{mL}\) sample of potassium iodide solution was analyzed by adding an excess of silver nitrate solution to produce silver iodide crystals, which were filtered from the solution. \(\mathrm{KI}(a q)+\mathrm{AgNO}_{3}(a q) \longrightarrow \mathrm{KNO}_{3}(a q)+\operatorname{AgI}(s)\) If \(2.183 \mathrm{~g}\) of silver iodide was obtained, what was the molarity of the original KI solution?

A \(25.0-\mathrm{mL}\) sample of sodium sulfate solution was analyzed by adding an excess of barium chloride solution to produce barium sulfate crystals, which were filtered from the solution. \(\mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+\mathrm{BaCl}_{2}(a q) \longrightarrow 2 \mathrm{NaCl}(a q)+\mathrm{BaSO}_{4}(s)\) If \(5.719 \mathrm{~g}\) of barium sulfate was obtained, what was the molarity of the original \(\mathrm{Na}_{2} \mathrm{SO}_{4}\) solution?

A metal, \(\mathrm{M}\), was converted to the sulfate, \(\mathrm{M}_{2}\left(\mathrm{SO}_{4}\right)_{3}\). Then a solution of the sulfate was treated with barium chloride to give barium sulfate crystals, which were filtered off. \(\mathrm{M}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+3 \mathrm{BaCl}_{2}(a q) \longrightarrow 2 \mathrm{MCl}_{3}(a q)+3 \mathrm{BaSO}_{4}(s)\) If \(1.200 \mathrm{~g}\) of the metal gave \(6.026 \mathrm{~g}\) of barium sulfate, what is the atomic weight of the metal? What is the metal?

A metal, \(\mathrm{M}\), was converted to the chloride, \(\mathrm{MCl}_{2} .\) Then a solution of the chloride was treated with silver nitrate to give silver chloride crystals, which were filtered from the solution. \(\mathrm{MCl}_{2}(a q)+2 \mathrm{AgNO}_{3}(a q) \longrightarrow \mathrm{M}\left(\mathrm{NO}_{3}\right)_{2}(a q)+2 \mathrm{AgCl}(s)\) If \(2.434 \mathrm{~g}\) of the metal gave \(7.964 \mathrm{~g}\) of silver chloride, what is the atomic weight of the metal? What is the metal?

Phosphoric acid is prepared by dissolving phosphorus(V) oxide, \(\mathrm{P}_{4} \mathrm{O}_{10}\), in water. What is the balanced equation for this reaction? How many grams of \(\mathrm{P}_{4} \mathrm{O}_{10}\) are required to make \(1.50 \mathrm{~L}\) of aqueous solution containing \(5.00 \%\) phosphoric acid by mass? The density of the solution is \(1.025 \mathrm{~g} / \mathrm{mL}\).

Iron(III) chloride can be prepared by reacting iron metal with chlorine. What is the balanced equation for this reaction? How many grams of iron are required to make \(3.00 \mathrm{~L}\) of aqueous solution containing \(9.00 \%\) iron(III) chloride by mass? The density of the solution is \(1.067 \mathrm{~g} / \mathrm{mL}\).

An alloy of aluminum and magnesium was treated with sodium hydroxide solution, in which only aluminum reacts. \(2 \mathrm{Al}(s)+2 \mathrm{NaOH}(a q)+6 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow{2 \mathrm{NaAl}(\mathrm{OH})_{4}(a q)+3 \mathrm{H}_{2}(g)}\) If a sample of alloy weighing \(1.118\) g gave \(0.1068 \mathrm{~g}\) of hydrogen, what is the percentage of aluminum in the alloy?

An alloy of iron and carbon was treated with sulfuric acid. in which only iron reacts. \(2 \mathrm{Fe}(s)+3 \mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow \mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+3 \mathrm{H}_{2}(g)\) If a sample of alloy weighing \(2.358\) g gave \(0.1152 \mathrm{~g}\) of hydro- gen, what is the percentage of iron in the alloy?

Determine the volume of sulfuric acid solution needed to prepare \(37.4 \mathrm{~g}\) of aluminum sulfate, \(\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}\), by the reaction \(2 \mathrm{Al}(s)+3 \mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+3 \mathrm{H}_{2}(g)\) The sulfuric acid solution, whose density is \(1.104 \mathrm{~g} / \mathrm{mL}\), contains \(15.0 \% \mathrm{H}_{2} \mathrm{SO}_{4}\) by mass.

Determine the volume of sodium hydroxide solution needed to prepare \(26.2 \mathrm{~g}\) sodium phosphate, \(\mathrm{Na}_{3} \mathrm{PO}_{4}\), by the reaction \(3 \mathrm{NaOH}(a q)+\mathrm{H}_{3} \mathrm{PO}_{4}(a q) \longrightarrow \mathrm{Na}_{3} \mathrm{PO}_{4}(a q)+3 \mathrm{H}_{2} \mathrm{O}(l)\) The sodium hydroxide solution, whose density is \(1.133 \mathrm{~g} / \mathrm{mL}\), contains \(12.0 \% \mathrm{NaOH}\) by mass.

The active ingredients of an antacid tablet contained only magnesium hydroxide and aluminum hydroxide. Complete neutralization of a sample of the active ingredients required \(48.5 \mathrm{~mL}\) of \(0.187 M\) hydrochloric acid. The chloride salts from this neutralization were obtained by evaporation of the filtrate from the titration; they weighed \(0.4200 \mathrm{~g}\). What was the percentage by mass of magnesium hydroxide in the active ingredients of the antacid tablet?

The active ingredients in an antacid tablet contained only calcium carbonate and magnesium carbonate. Complete reaction of a sample of the active ingredients required \(41.33 \mathrm{~mL}\) of \(0.08750 M\) hydrochloric acid. The chloride salts from the reaction were obtained by evaporation of the filtrate from this titration; they weighed \(0.1900 \mathrm{~g}\). What was the percentage by mass of the calcium carbonate in the active ingredients of the antacid tablet?