Chapter 3

Balance the following equations, and then classify each as a precipitation, acid-base, or gas-forming reaction. Show states for the products (s, \(\ell, \mathrm{g},\) aq), and then balance the completed equation. Write the net ionic equation. (a) \(\mathrm{Fe}(\mathrm{OH})_{3}(\mathrm{s})+\mathrm{HNO}_{3}(\mathrm{aq}) \rightarrow \mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3}+\mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{FeCO}_{3}(\mathrm{s})+\mathrm{HNO}_{3}(\mathrm{aq}) \rightarrow \mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}\)

Balance each of the following equations, and classify them as precipitation, acid-base, gas-forming, or oxidation-reduction reactions. Show states for the products \((\mathrm{s}, \ell, \mathrm{g}, \mathrm{aq}),\) and then balance the completed equation. (a) \(\mathrm{CuCl}_{2}+\mathrm{H}_{2} \mathrm{S} \rightarrow \mathrm{CuS}+\mathrm{HCl}\) (b) \(\mathrm{H}_{3} \mathrm{PO}_{4}+\mathrm{KOH} \rightarrow \mathrm{H}_{2} \mathrm{O}+\mathrm{K}_{3} \mathrm{PO}_{4}\) (c) \(\mathrm{Ca}+\mathrm{HBr} \rightarrow \mathrm{H}_{2}+\mathrm{CaBr}_{2}\) (d) \(\mathrm{MgCl}_{2}+\mathrm{NaOH} \rightarrow \mathrm{Mg}(\mathrm{OH})_{2}+\mathrm{NaCl}\)

Complete and balance the equations below, and classify them as precipitation, acid-base, gas-forming, or oxidation-reduction reactions. Show states for the products \((\mathrm{s}, \ell, \mathrm{g}, \mathrm{aq}),\) and then balance the completed equation. (a) \(\mathrm{NiCO}_{3}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow\) (b) \(\mathrm{Co}(\mathrm{OH})_{2}+\mathrm{HBr} \rightarrow\) (c) \(\mathrm{AgCH}_{3} \mathrm{CO}_{2}+\mathrm{NaCl} \rightarrow\) (d) \(\mathrm{NiO}+\mathrm{CO} \rightarrow\)

Balance the following equations: (a) for the synthesis of urea, a common fertilizer \(\mathrm{CO}_{2}(\mathrm{g})+\mathrm{NH}_{3}(\mathrm{g}) \rightarrow \mathrm{NH}_{2} \mathrm{CONH}_{2}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\ell)\) (b) for the reactions used to make uranium(VI) fluoride for the enrichment of natural uranium \(\mathrm{UO}_{2}(\mathrm{s})+\mathrm{HF}(\mathrm{aq}) \rightarrow \mathrm{UF}_{4}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\ell)\) \(\mathrm{UF}_{4}(\mathrm{s})+\mathrm{F}_{2}(\mathrm{g}) \rightarrow \mathrm{UF}_{6}(\mathrm{s})\) (c) for the reaction to make titanium(IV) chloride, which is then converted to titanium metal \(\mathrm{TiO}_{2}(\mathrm{s})+\mathrm{Cl}_{2}(\mathrm{g})+\mathrm{C}(\mathrm{s}) \rightarrow \mathrm{TiCl}_{4}(\ell)+\mathrm{CO}(\mathrm{g})\) \(\operatorname{TiCl}_{4}(\ell)+\operatorname{Mg}(\mathrm{s}) \rightarrow \operatorname{Ti}(\mathrm{s})+\operatorname{Mg} \mathrm{Cl}_{2}(\mathrm{s})\)

Balance the following equations: (a) for the reaction to produce "superphosphate" fertilizer \(\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}(\mathrm{s})+\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq}) \rightarrow \mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2}(\mathrm{aq})+\mathrm{CaSO}_{4}(\mathrm{s})\) (b) for the reaction to produce diborane, \(\mathrm{B}_{2} \mathrm{H}_{6}\) \(\begin{aligned} \mathrm{NaBH}_{4}(\mathrm{s})+\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq}) & \rightarrow \\ & \mathrm{B}_{2} \mathrm{H}_{6}(\mathrm{g})+\mathrm{H}_{2}(\mathrm{g})+\mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq}) \end{aligned}\) (c) for the reaction to produce tungsten metal from tungsten(VI) oxide \(\mathrm{WO}_{3}(\mathrm{s})+\mathrm{H}_{2}(\mathrm{g}) \rightarrow \mathrm{W}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\ell)\) (d) for the decomposition of ammonium dichromate \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}(\mathrm{s}) \rightarrow \mathrm{N}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\ell)+\mathrm{Cr}_{2} \mathrm{O}_{3}(\mathrm{s})\)

Give a formula for each of the following compounds: (a) a soluble compound containing the bromide ion (b) an insoluble hydroxide (c) an insoluble carbonate (d) a soluble nitrate-containing compound (e) a weak Bronsted acid

Indicate which of the following copper(II) salts are soluble in water and which are insoluble: \(\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}\) \(\mathrm{CuCO}_{3}, \mathrm{Cu}_{3}\left(\mathrm{PO}_{4}\right)_{2}, \mathrm{CuCl}_{2}\).

Write the net ionic equation and identify the spectator ion or ions in the reaction of nitric acid and magnesium hydroxide. What type of reaction is this? $$\begin{array}{rl} 2 \mathrm{H}_{3} \mathrm{O}^{+}(\mathrm{aq})+2 \mathrm{NO}_{3}^{-}(\mathrm{aq})+\mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{s}) & \rightarrow \\ 4 \mathrm{H}_{2} \mathrm{O}(\ell)+\mathrm{Mg}^{2+}(\mathrm{aq})+2 & \mathrm{NO}_{3}^{-}(\mathrm{aq}) \end{array}$$

Identify and name the water-insoluble product in each reaction and write the net ionic equation: (a) \(\operatorname{CuCl}_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{S}(\mathrm{aq}) \rightarrow \mathrm{CuS}+2 \mathrm{HCl}\) (b) \(\mathrm{CaCl}_{2}(\mathrm{aq})+\mathrm{K}_{2} \mathrm{CO}_{3}(\mathrm{aq}) \rightarrow 2 \mathrm{KCl}+\mathrm{CaCO}_{3}\) (c) \(\mathrm{AgNO}_{3}(\mathrm{aq})+\mathrm{NaI}(\mathrm{aq}) \rightarrow \mathrm{AgI}+\mathrm{NaNO}_{3}\)

Bromine is obtained from sea water by the following redox reaction: $$\mathrm{Cl}_{2}(\mathrm{g})+2 \mathrm{NaBr}(\mathrm{aq}) \rightarrow 2 \mathrm{NaCl}(\mathrm{aq})+\mathrm{Br}_{2}(\ell)$$ (a) What has been oxidized? What has been reduced? (b) Identify the oxidizing and reducing agents.

Identify each of the following substances as a likely oxidizing or reducing agent: \(\mathrm{HNO}_{3}, \mathrm{Na}, \mathrm{Cl}_{2}, \mathrm{O}_{2} \mathrm{KMnO}_{4}\).

The mineral dolomite contains magnesium carbonate. This reacts with hydrochloric acid. $$\mathrm{MgCO}_{3}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{CO}_{2}(\mathrm{g})+\mathrm{MgCl}_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\ell)$$ (a) Write the net ionic equation for this reaction and identify the spectator ions. (b) What type of reaction is this?

Aqueous solutions of ammonium sulfide, \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{S},\) and \(\mathrm{Hg}\left(\mathrm{NO}_{3}\right)_{2}\) react to produce HgS and \(\mathrm{NH}_{4} \mathrm{NO}_{3}\). (a) Write the overall balanced equation for the reaction. Indicate the state (s, aq) for each compound. (b) Name each compound. (c) What type of reaction is this?

Identify the primary species (atoms, molecules, or ions) present in an aqueous solution of each of the following compounds. Decide which species are Bronsted acids or bases and whether they are strong or weak. (b) \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\) (a) \(\mathrm{NH}_{3}\) (c) \(\mathrm{NaOH}\) (d) HBr

(a) Name and give formulas for two water-soluble compounds containing the \(\mathrm{Cu}^{2+}\) ion. Name two waterinsoluble compounds containing the \(\mathrm{Cu}^{2+}\) ion. (b) Name and give formulas for two water-soluble compounds containing the \(\mathrm{Ba}^{2+}\) ion. Name two waterinsoluble compounds containing the \(\mathrm{Ba}^{2+}\) ion.

Balance equations for these reactions that occur in aqueous solution, and then classify each as a precipitation, acid-base, or gas-forming reaction. Show states for the products \((\mathrm{s}, \ell, \mathrm{g}, \mathrm{aq}),\) give their names, and write the net ionic equation. (a) \(\mathrm{K}_{2} \mathrm{CO}_{3}+\mathrm{HClO}_{4} \rightarrow \mathrm{KClO}_{4}+\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{FeCl}_{2}+\left(\mathrm{NH}_{4}\right)_{2} \mathrm{S} \rightarrow \mathrm{FeS}+\mathrm{NH}_{4} \mathrm{Cl}\) (c) \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{aq}) \rightarrow \mathrm{FeCO}_{3}+\mathrm{NaNO}_{3}\) (d) \(\mathrm{NaOH}+\mathrm{FeCl}_{3} \rightarrow \mathrm{NaCl}+\mathrm{Fe}(\mathrm{OH})_{3}\)

For each reaction, write an overall, balanced equation and the net ionic equation. (a) the reaction of aqueous lead(II) nitrate and aqueous potassium hydroxide (b) the reaction of aqueous copper(II) nitrate and aqueous sodium carbonate

You are given mixtures containing the following compounds. Which compound in each pair could be separated by stirring the solid mixture with water? (a) \(\mathrm{NaOH}\) and \(\mathrm{Ca}(\mathrm{OH})_{2}\) (b) \(\mathrm{MgCl}_{2}\) and \(\mathrm{MgF}_{2}\) (c) AgI and KI (d) \(\mathrm{NH}_{4} \mathrm{Cl}\) and \(\mathrm{PbCl}_{2}\)

Identify, from each list below, the compound or compounds that will dissolve in water to give a solution that strongly conducts electricity. (a) \(\mathrm{CuCO}_{3}, \mathrm{Cu}(\mathrm{OH})_{2}, \mathrm{CuCl}_{2}, \mathrm{CuO}\) (b) \(\mathrm{HCl}, \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}, \mathrm{H}_{3} \mathrm{PO}_{4}, \mathrm{H}_{2} \mathrm{SO}_{4}\)

Identify, from each list below, the compound or compounds that will dissolve in water to give a solution that is only a very weak conductor of electricity. (a) \(\mathrm{NH}_{3}, \mathrm{NaOH}, \mathrm{Ba}(\mathrm{OH})_{2}, \mathrm{Fe}(\mathrm{OH})_{3}\) (b) \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}, \mathrm{Na}_{3} \mathrm{PO}_{4}, \mathrm{HF}, \mathrm{HNO}_{3}\)

Write net ionic equations for the following reactions: (a) The reaction of acetic acid, a weak acid, and \(\mathrm{Sr}(\mathrm{OH})_{2}(\mathrm{aq})\) (b) The reaction of zinc and hydrochloric acid to form zinc(II) chloride and hydrogen gas.

Gas evolution was observed when a solution of \(\mathrm{Na}_{2} \mathrm{S}\) was treated with acid. The gas was bubbled into a solution containing \(\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2},\) and a black precipitate formed. Write net ionic equations for the two reactions.

Heating \(\mathrm{HI}(\mathrm{g})\) at \(425^{\circ} \mathrm{C}\) causes some of this compound to decompose, forming \(\mathrm{H}_{2}(\mathrm{g})\) and \(\mathrm{I}_{2}(\mathrm{g}) .\) Eventually, the amounts of the three species do not change further; the system has reached equilibrium. (At this point, approximately \(22 \%\) of the HI has decomposed.) Describe what is happening in this system at the molecular level.

The following reaction can be used to prepare iodine in the laboratory. $$\begin{aligned}2 \mathrm{NaI}(\mathrm{s}) &+2 \mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq})+\mathrm{MnO}_{2}(\mathrm{s}) \rightarrow \\\& \mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq})+\mathrm{MnSO}_{4}(\mathrm{aq})+\mathrm{I}_{2}(\mathrm{g})+2 \mathrm{H}_{2} \mathrm{O}(\ell)\end{aligned}$$ (a) Determine the oxidation number of each atom in the equation. (b) What is the oxidizing agent, and what has been oxidized? What is the reducing agent, and what has been reduced? (c) Is the reaction observed product-favored or reactant-favored? (d) Name the reactants and products.

Suppose you wish to prepare a sample of magnesium chloride. One way to do this is to use an acid-base reaction, the reaction of magnesium hydroxide with hydrochloric acid. $$\mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{MgCl}_{2}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\ell)$$ When the reaction is complete, evaporating the water will give solid magnesium chloride. Suggest at least one other way to prepare \(\mathrm{MgCl}_{2}\).

You want to prepare barium chloride, \(\mathrm{BaCl}_{2},\) using an exchange reaction of some type. To do so, you have the following reagents from which to select the reactants: \(\mathrm{BaSO}_{4}, \mathrm{BaBr}_{2}, \mathrm{BaCO}_{3}, \mathrm{Ba}(\mathrm{OH})_{2}, \mathrm{HCl}, \mathrm{HgSO}_{4}, \mathrm{AgNO}_{3}\) and HNO \(_{3} .\) Write a complete, balanced equation for the reaction chosen. (Note: There are several possibilities.)

Describe how to prepare \(\mathrm{BaSO}_{4},\) barium sulfate, by (a) a precipitation reaction and (b) a gas-forming reaction. To do so, you have the following reagents from which to select the reactants: \(\mathrm{BaCl}_{2}, \mathrm{BaCO}_{3}, \mathrm{Ba}(\mathrm{OH})_{2}\) \(\mathrm{H}_{2} \mathrm{SO}_{4},\) and \(\mathrm{Na}_{2} \mathrm{SO}_{4} .\) Write complete, balanced equations for the reactions chosen. (See page 127 for an illustration of the preparation of a compound.)

Describe how to prepare zinc chloride by (a) an acid-base reaction, (b) a gas- forming reaction, and (c) an oxidation-reduction reaction. The available starting materials are \(\mathrm{ZnCO}_{3}, \mathrm{HCl}, \mathrm{Cl}_{2}, \mathrm{HNO}_{3}\) \(\mathrm{Zn}(\mathrm{OH})_{2}, \mathrm{NaCl}, \mathrm{Zn}\left(\mathrm{NO}_{3}\right)_{2},\) and \(\mathrm{Zn} .\) Write complete balanced equations for the reactions chosen.

A common method for analyzing for the nickel content of a sample is to use a precipitation reaction. Adding the organic compound dimethylglyoxime to a solution containing \(\mathrm{Ni}^{2+}\) ions, precipitates a red solid. Derive the empirical formula for the red solid based on the following composition: \(\mathrm{Ni}, 20.315 \% ; \mathrm{C}, 33.258 \% ; \mathrm{H}\) \(4.884 \% ; \mathbf{O}, 22.151 \% ;\) and \(\mathrm{N}, 19.392 \%\).

The lanthanide elements react with oxygen to give, generally, compounds of the type \(\mathrm{Ln}_{2} \mathrm{O}_{3}\) (where Ln stands for a lanthanide element). However, there are interesting exceptions, such as a common oxide of terbium, \(\mathrm{Tb}_{\mathrm{x}} \mathrm{O}_{y}\). Given that the compound is \(73.945 \%\) Tb, what is its formula? What is the oxidation number of terbium in this compound? Write a balanced equation for the reaction of terbium and oxygen to give this oxide.

The presence of arsenic in a sample that may also contain another Group 5 A element, antimony, can be confirmed by first precipitating the \(\mathrm{As}^{3+}\) and \(\mathrm{Sb}^{3+}\) ions as yellow solid \(\mathrm{As}_{2} \mathrm{S}_{3}\) and orange solid \(\mathrm{Sb}_{2} \mathrm{S}_{3} .\) If aqueous HCl is then added, only \(\mathrm{Sb}_{2} \mathrm{S}_{3}\) dissolves, leaving behind solid \(\mathrm{As}_{2} \mathrm{S}_{3} .\) The \(\mathrm{As}_{2} \mathrm{S}_{3}\) can then be dissolved using aqueous HNO \(_{3}\) $$\begin{aligned} 3 \mathrm{As}_{2} \mathrm{S}_{3}(\mathrm{s})+10 \mathrm{HNO}_{3}(\mathrm{aq})+4 \mathrm{H}_{2} \mathrm{O}(\ell) & \rightarrow \\ 6 \mathrm{H}_{3} \mathrm{AsO}_{4}(\mathrm{aq})+10 \mathrm{NO}(\mathrm{g})+9 \mathrm{S}(\mathrm{s}) \end{aligned}$$ Finally, the presence of arsenic is confirmed by adding \(\mathrm{AgNO}_{3}\) to the solution of \(\mathrm{H}_{3} \mathrm{AsO}_{4}\) to precipitate a reddish brown solid \(\mathrm{Ag}_{x} \mathrm{AsO}_{y} .\) The composition of this solid is As, \(16.199 \%\) and \(\mathrm{Ag}, 69.964 \%\) (a) What are the oxidation numbers of As, \(S,\) and \(N\) in the reaction of \(\mathrm{As}_{2} \mathrm{S}_{3}\) with nitric acid? (b) What is the formula of the reddish brown solid \(\mathrm{Ag}_{\mathrm{x}} \mathrm{A} \mathrm{s} \mathrm{O}_{\mathrm{y}} ?\)