Chapter 4

Obtain the oxidation number for the element noted in each of the following. a. Ga in \(\mathrm{Ga}_{2} \mathrm{O}_{3}\) b. \(\mathrm{Nb}\) in \(\mathrm{NbO}_{2}\) c. Br in \(\mathrm{KBrO}_{4}\) d. \(\mathrm{Mn}\) in \(\mathrm{K}_{2} \mathrm{MnO}_{4}\)

Obtain the oxidation number for the element noted in each of the following. a. Cr in \(\mathrm{CrO}_{3}\) b. \(\mathrm{Hg}\) in \(\mathrm{Hg}_{2} \mathrm{Cl}_{2}\) c. Ga in \(\mathrm{Ga}(\mathrm{OH})_{3}\) d. \(\mathrm{P}\) in \(\mathrm{Na}_{3} \mathrm{PO}_{4}\)

Obtain the oxidation number for the element noted in each of the following. a. \(\mathrm{N}\) in \(\mathrm{NH}_{2}\) b. I in \(\mathrm{IO}_{3}^{-}\) C. \(\mathrm{Al}\) in \(\mathrm{Al}(\mathrm{OH})_{4}^{-}\) d. \(\mathrm{Cl}\) in \(\mathrm{HClO}_{4}\)

Obtain the oxidation number for the element noted in each of the following. a. \(\mathrm{N}\) in \(\mathrm{NO}_{2}^{-}\) b. \(\mathrm{Cr}\) in \(\mathrm{Cr} \mathrm{O}_{4}^{2-}\) c. \(\mathrm{Zn}\) in \(\mathrm{Zn}(\mathrm{OH})_{4}{\underline{\phantom{xx}}}^{2-}\) d. As in \(\mathrm{H}_{2} \mathrm{As} \mathrm{O}_{3}^{-}\)

Determine the oxidation numbers of all the elements in each of the following compounds. (Hint: Look at the ions present.) a. \(\mathrm{Mn}\left(\mathrm{ClO}_{3}\right)_{2}\) b. \(\mathrm{Fe}_{2}\left(\mathrm{CrO}_{4}\right)_{3}\) c. \(\mathrm{HgCr}_{2} \mathrm{O}_{7}\) d. \(\mathrm{Co}_{3}\left(\mathrm{PO}_{4}\right)_{2}\)

Determine the oxidation numbers of all the elements in each of the following compounds. (Hint: Look at the ions present.) a. \(\mathrm{Hg}_{2}\left(\mathrm{BrO}_{3}\right)_{2}\) b. \(\mathrm{Cr}_{2}\left(\mathrm{SO}_{4}\right)_{3}\) c. \(\operatorname{CoSeO}_{4}\) d. \(\mathrm{Pb}(\mathrm{OH})_{2}\)

In the following reactions, label the oxidizing agent and the reducing agent. a. \(\mathrm{P}_{4}(s)+5 \mathrm{O}_{2}(g) \longrightarrow \mathrm{P}_{4} \mathrm{O}_{10}(s)\) b. \(\mathrm{Co}(s)+\mathrm{Cl}_{2}(g) \longrightarrow \mathrm{CoCl}_{2}(s)\)

In the following reactions, label the oxidizing agent and the reducing agent. a. \(\mathrm{ZnO}(s)+\mathrm{C}(s) \longrightarrow \mathrm{Zn}(g)+\mathrm{CO}(g)\) b. \(8 \mathrm{Fe}(s)+\mathrm{S}_{8}(s) \longrightarrow 8 \mathrm{FeS}(s)\)

In the following reactions, label the oxidizing agent and the reducing agent. a. \(2 \mathrm{Al}(s)+3 \mathrm{~F}_{2}(g) \longrightarrow 2 \mathrm{AlF}_{3}(s)\) b. \(\mathrm{Hg}^{2+}(a q)+\mathrm{NO}_{2}^{-}(a q)+\mathrm{H}_{2} \mathrm{O}(I) \longrightarrow\) $$ \mathrm{Hg}(s)+2 \mathrm{H}^{+}(a q)+\mathrm{NO}_{3}^{-}(a q) $$

In the following reactions, label the oxidizing agent and the reducing agent. a. \(\mathrm{Fe}_{2} \mathrm{O}_{3}(s)+3 \mathrm{CO}(g) \longrightarrow 2 \mathrm{Fe}(s)+3 \mathrm{CO}_{2}(g)\) b. \(\mathrm{PbS}(s)+4 \mathrm{H}_{2} \mathrm{O}_{2}(a q) \longrightarrow \mathrm{PbSO}_{4}(s)+4 \mathrm{H}_{2} \mathrm{O}(l)\)

Balance the following oxidation-reduction reactions by the half-reaction method. a. \(\mathrm{CuCl}_{2}(a q)+\mathrm{Al}(s) \longrightarrow \mathrm{AlCl}_{3}(a q)+\mathrm{Cu}(s)\) b. \(\mathrm{Cr}^{3+}(a q)+\mathrm{Zn}(s) \longrightarrow \mathrm{Cr}(s)+\mathrm{Zn}^{2+}(a q)\)

Balance the following oxidation-reduction reactions by the half-reaction method. a. \(\mathrm{FeI}_{3}(a q)+\mathrm{Mg}(s) \longrightarrow \mathrm{Fe}(s)+\mathrm{MgI}_{2}(a q)\) b. \(\mathrm{H}_{2}(g)+\mathrm{Ag}^{+}(a q) \longrightarrow \mathrm{Ag}(s)+\mathrm{H}^{+}(a q)\)

A sample of \(0.0512\) mol of iron(III) chloride, \(\mathrm{FeCl}_{3}\), was dissolved in water to give \(25.0 \mathrm{~mL}\) of solution. What is the molarity of the solution?

A \(50.0-\mathrm{mL}\) volume of \(\mathrm{AgNO}_{3}\) solution contains \(0.0285\) mol \(\mathrm{AgNO}_{3}\) (silver nitrate). What is the molarity of the solution?

An aqueous solution is made from \(0.798 \mathrm{~g}\) of potassium permanganate, \(\mathrm{KMnO}_{4}\). If the volume of solution is \(50.0 \mathrm{~mL}\), what is the molarity of \(\mathrm{KMnO}_{4}\) in the solution?

A sample of oxalic acid, \(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\), weighing \(1.192 \mathrm{~g}\) is placed in a \(100.0-\mathrm{mL}\) volumetric flask, which is then filled to the mark with water. What is the molarity of the solution?

What volume of \(0.120 \mathrm{M} \mathrm{CuSO}_{4}\) is required to give \(0.150\) mol of copper(II) sulfate, \(\mathrm{CuSO}_{4}\) ?

How many milliliters of \(0.126 \mathrm{M} \mathrm{HClO}_{4}\) (perchloric acid) are required to give \(0.102 \mathrm{~mol} \mathrm{HClO}_{4}\) ?

An experiment calls for \(0.0353 \mathrm{~g}\) of potassium hydroxide, KOH. How many milliliters of \(0.0176 \mathrm{M} \mathrm{KOH}\) are required?

What is the volume (in milliliters) of \(0.215 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}\) (sulfuric acid) containing \(0.949 \mathrm{~g} \mathrm{H}_{2} \mathrm{SO}_{4}\) ?

Heme, obtained from red blood cells, binds oxygen, \(\mathrm{O}_{2}\). How many moles of heme are there in \(150 \mathrm{~mL}\) of \(0.0019 M\) heme solution?

Insulin is a hormone that controls the use of glucose in the body. How many moles of insulin are required to make up \(28 \mathrm{~mL}\) of \(0.0048 \mathrm{M}\) insulin solution?

How many grams of sodium dichromate, \(\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\), should be added to a \(100.0-\mathrm{mL}\) volumetric flask to prepare \(0.025 \mathrm{M} \mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) when the flask is filled to the mark with water?

Describe how you would prepare \(2.50 \times 10^{2} \mathrm{~mL}\) of \(0.20\) \(M \mathrm{Na}_{2} \mathrm{SO}_{4} .\) What mass (in grams) of sodium sulfate, \(\mathrm{Na}_{2} \mathrm{SO}_{4}\), is needed?

You wish to prepare \(0.12 \mathrm{M} \mathrm{HNO}_{3}\) from a stock solution of nitric acid that is \(15.8 \mathrm{M}\). How many milliliters of the stock solution do you require to make up \(1.00 \mathrm{~L}\) of \(0.12 \mathrm{M}\) \(\mathrm{HNO}_{3} ?\)

A chemist wants to prepare \(0.50 M\) HCl. Commercial hydrochloric acid is \(12.4 M\). How many milliliters of the commercial acid does the chemist require to make up \(1.50 \mathrm{~L}\) of the dilute acid?

A \(3.50 \mathrm{~g}\) sample of \(\mathrm{KCl}\) is dissolved in \(10.0 \mathrm{~mL}\) of water. The resulting solution is then added to \(60.0 \mathrm{~mL}\) of a \(0.500 \mathrm{M}\) \(\mathrm{CaCl}_{2}(a q)\) solution. Assuming that the volumes are additive, calculate the concentrations of each ion present in the final solution.

Calculate the concentrations of each ion present in a solution that results from mixing \(50.0 \mathrm{~mL}\) of a \(0.20 \mathrm{M} \mathrm{NaClO}_{3}(a q)\) solution with \(25.0 \mathrm{~mL}\) of a \(0.20 \mathrm{M} \mathrm{Na}_{2} \mathrm{SO}_{4}(a q)\). Assume that the volumes are additive.

A chemist added an excess of sodium sulfate to a solution of a soluble barium compound to precipitate all of the barium ion as barium sulfate, \(\mathrm{BaSO}_{4}\). How many grams of barium ion are in a \(458-\mathrm{mg}\) sample of the barium compound if a solution of the sample gave \(513 \mathrm{mg} \mathrm{BaSO}_{4}\) precipitate? What is the mass percentage of barium in the compound?

A soluble iodide was dissolved in water. Then an excess of silver nitrate, \(\mathrm{AgNO}_{3}\), was added to precipitate all of the iodide ion as silver iodide, AgI. If \(1.545 \mathrm{~g}\) of the soluble iodide gave \(2.185 \mathrm{~g}\) of silver iodide, how many grams of iodine are in the sample of soluble iodide? What is the mass percentage of iodine, \(\mathrm{I}\), in the compound?

Copper has compounds with copper(I) ion or copper(II) ion. A compound of copper and chlorine was treated with a solution of silver nitrate, \(\mathrm{AgNO}_{3}\), to convert the chloride ion in the compound to a precipitate of AgCl. A \(59.40-\mathrm{mg}\) sample of the copper compound gave \(86.00 \mathrm{mg} \mathrm{AgCl}\). a. Calculate the percentage of chlorine in the copper compound. b. Decide whether the formula of the compound is \(\mathrm{CuCl}\) or \(\mathrm{CuCl}_{2}\)

Gold has compounds containing gold(I) ion or gold(III) ion. A compound of gold and chlorine was treated with a solution of silver nitrate, \(\mathrm{AgNO}_{3}\), to convert the chloride ion in the compound to a precipitate of AgCl. A \(162.7-\mathrm{mg}\) sample of the gold compound gave \(100.3 \mathrm{mg} \mathrm{AgCl}\). a. Calculate the percentage of the chlorine in the gold compound. b. Decide whether the formula of the compound is \(\mathrm{AuCl}\) or \(\mathrm{AuCl}_{3}\)

A compound of iron and chlorine is soluble in water. An excess of silver nitrate was added to precipitate the chloride ion as silver chloride. If a \(134.8-\mathrm{mg}\) sample of the compound gave \(304.8 \mathrm{mg} \mathrm{AgCl}\), what is the formula of the compound?

A \(1.345-\mathrm{g}\) sample of a compound of barium and oxygen was dissolved in hydrochloric acid to give a solution of barium ion, which was then precipitated with an excess of potassium chromate to give \(2.012 \mathrm{~g}\) of barium chromate, \(\mathrm{BaCrO}_{4}\). What is the formula of the compound?

What volume of \(0.250 \mathrm{M} \mathrm{HNO}_{3}\) (nitric acid) reacts with \(44.8 \mathrm{~mL}\) of \(0.150 \mathrm{M} \mathrm{Na}_{2} \mathrm{CO}_{3}\) (sodium carbonate) in the following reaction? $$ 2 \mathrm{HNO}_{3}(a q)+\mathrm{Na}_{2} \mathrm{CO}_{3}(a q) \longrightarrow{2 \mathrm{NaNO}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{CO}_{2}(g)} $$

A flask contains \(49.8 \mathrm{~mL}\) of \(0.150 \mathrm{M} \mathrm{Ca}(\mathrm{OH})_{2}\) (calcium hydroxide). How many milliliters of \(0.350 \mathrm{M} \mathrm{Na}_{2} \mathrm{CO}_{3}\) (sodium carbonate) are required to react completely with the calcium hydroxide in the following reaction? $$ \mathrm{Na}_{2} \mathrm{CO}_{3}(a q)+\mathrm{Ca}(\mathrm{OH})_{2}(a q) \longrightarrow \mathrm{CaCO}_{3}(s)+2 \mathrm{NaOH}(a q) $$

How many milliliters of \(0.150 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}\) (sulfuric acid) are required to react with \(8.20 \mathrm{~g}\) of sodium hydrogen carbonate, \(\mathrm{NaHCO}_{3}\), according to the following equation? \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+2 \mathrm{NaHCO}_{3}(a q) \longrightarrow\) $$ \mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l)+2 \mathrm{CO}_{2}(g) $$

How many milliliters of \(0.250 \mathrm{M} \mathrm{KMnO}_{4}\) are needed to react with \(3.36 \mathrm{~g}\) of iron(II) sulfate, \(\mathrm{FeSO}_{4}\) ? The reaction is as follows: $$ \begin{aligned} &10 \mathrm{FeSO}_{4}(a q)+2 \mathrm{KMnO}_{4}(a q)+8 \mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow \\ &5 \mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+2 \mathrm{MnSO}_{4}(a q)+\mathrm{K}_{2} \mathrm{SO}_{4}(a q)+8 \mathrm{H}_{2} \mathrm{O}(l) \end{aligned} $$

A \(3.33-\mathrm{g}\) sample of iron ore is transformed to a solution of iron(II) sulfate, \(\mathrm{FeSO}_{4}\), and this solution is titrated with \(0.150 \mathrm{M} \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) (potassium dichromate). If it requires \(43.7 \mathrm{~mL}\) of potassium dichromate solution to titrate the iron(II) sulfate solution, what is the percentage of iron in the ore? The reaction is $$ \begin{aligned} &6 \mathrm{FeSO}_{4}(a q)+\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}(a q)+7 \mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow \\ &3 \mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+\mathrm{Cr}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+7 \mathrm{H}_{2} \mathrm{O}(I)+\mathrm{K}_{2} \mathrm{SO}_{4}(a q) \end{aligned} $$

Magnesium metal reacts with hydrobromic acid to produce hydrogen gas and a solution of magnesium bromide. Write the molecular equation for this reaction. Then write the corresponding net ionic equation.

Aluminum metal reacts with perchloric acid to produce hydrogen gas and a solution of aluminum perchlorate. Write the molecular equation for this reaction. Then write the corresponding net ionic equation.

Nickel(II) sulfate solution reacts with lithium hydroxide solution to produce a precipitate of nickel(II) hydroxide and a solution of lithium sulfate. Write the molecular equation for this reaction. Then write the corresponding net ionic equation.

Potassium sulfate solution reacts with barium bromide solution to produce a precipitate of barium sulfate and a solution of potassium bromide. Write the molecular equation for this reaction. Then write the corresponding net ionic equation.

Decide whether a reaction occurs for each of the following. If it does not, write \(N R\) after the arrow. If it does, write the balanced molecular equation; then write the net ionic equation. a. \(\mathrm{LiOH}+\mathrm{HCN} \longrightarrow\) b. \(\mathrm{Li}_{2} \mathrm{CO}_{3}+\mathrm{HNO}_{3} \longrightarrow\) C. \(\mathrm{LiCl}+\mathrm{AgNO}_{3} \longrightarrow\) d. \(\mathrm{LiCl}+\mathrm{MgSO}_{4} \longrightarrow\)

Decide whether a reaction occurs for each of the following. If it does not, write \(N R\) after the arrow. If it does, write the balanced molecular equation; then write the net ionic equation. a. \(\mathrm{Al}(\mathrm{OH})_{3}+\mathrm{HNO}_{3} \longrightarrow\) b. \(\mathrm{NaBr}+\mathrm{HClO}_{4} \longrightarrow\) c. \(\mathrm{CaCl}_{2}+\mathrm{NaNO}_{3} \longrightarrow\) d. \(\mathrm{MgSO}_{4}+\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2} \longrightarrow\)

Complete and balance each of the following molecular equations, including phase labels, if a reaction occurs. Then write the net ionic equation. If no reaction occurs, write \(N R\) after the arrow. a. \(\mathrm{Sr}(\mathrm{OH})_{2}+\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2} \longrightarrow\) b. \(\mathrm{NH}_{4} \mathrm{I}+\mathrm{CsCl} \longrightarrow\) C. \(\mathrm{NaNO}_{3}+\mathrm{CsCl} \longrightarrow\) d. \(\mathrm{NH}_{4} \mathrm{I}+\mathrm{Ag} \mathrm{NO}_{3} \longrightarrow\)

Complete and balance each of the following molecular equations, including phase labels, if a reaction occurs. Then write the net ionic equation. If no reaction occurs, write \(N R\) after the arrow. a. \(\mathrm{HClO}_{4}+\mathrm{BaCO}_{3} \longrightarrow\) b. \(\mathrm{H}_{2} \mathrm{CO}_{3}+\mathrm{Sr}(\mathrm{OH})_{2} \longrightarrow\) c. \(\mathrm{K}_{3} \mathrm{PO}_{4}+\mathrm{MgCl}_{2} \longrightarrow\) d. \(\mathrm{FeSO}_{4}+\mathrm{MgCl}_{2} \longrightarrow\)

Describe in words how you would do each of the following preparations. Then give the molecular equation for each preparation. a. \(\mathrm{CuCl}_{2}(s)\) from \(\mathrm{CuSO}_{4}(s)\) b. \(\mathrm{Ca}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{2}(s)\) from \(\mathrm{CaCO}_{3}(s)\) c. \(\mathrm{NaNO}_{3}(s)\) from \(\mathrm{Na}_{2} \mathrm{SO}_{3}(s)\) d. \(\mathrm{MgCl}_{2}(s)\) from \(\mathrm{Mg}(\mathrm{OH})_{2}(s)\)

Describe in words how you would do each of the following preparations. Then give the molecular equation for each preparation. a. \(\mathrm{MgCl}_{2}(s)\) from \(\mathrm{MgCO}_{3}(s)\) b. \(\mathrm{NaNO}_{3}(s)\) from \(\mathrm{NaCl}(s)\) c. \(\mathrm{Al}(\mathrm{OH})_{3}(s)\) from \(\mathrm{Al}\left(\mathrm{NO}_{3}\right)_{3}(s)\) d. \(\mathrm{HCl}(a q)\) from \(\mathrm{H}_{2} \mathrm{SO}_{4}(a q)\)

Classify each of the following reactions as a combination reaction, decomposition reaction, displacement reaction, or combustion reaction. a. When they are heated, ammonium dichromate crystals, \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\), decompose to give nitrogen, water vapor, and solid chromium(III) oxide, \(\mathrm{Cr}_{2} \mathrm{O}_{3}\). b. When aqueous ammonium nitrite, \(\mathrm{NH}_{4} \mathrm{NO}_{2}\), is heated, it gives nitrogen and water vapor. C. When gaseous ammonia, \(\mathrm{NH}_{3}\), reacts with hydrogen chloride gas, HCl, fine crystals of ammonium chloride, \(\mathrm{NH}_{4} \mathrm{Cl}\), are formed. d. Aluminum added to an aqueous solution of sulfuric acid, \(\mathrm{H}_{2} \mathrm{SO}_{4}\), forms a solution of aluminum sulfate, \(\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3} .\) Hydrogen gas is released.