Chapter 20

Write a balanced equation to represent the electrolysis of molten sodium chloride. What volume of \(\mathrm{Cl}_{2}\) at STP is formed at the anode when \(1.00 \mathrm{~g}\) of sodium is formed at the cathode?

Write a balanced equation to represent the electrolysis of aluminum oxide. If \(2.00 \mathrm{~L}\) of \(\mathrm{O}_{2}\) at \(25^{\circ} \mathrm{C}\) and \(751 \mathrm{~mm} \mathrm{Hg}\) is formed at the anode, what mass of \(\mathrm{Al}\) is formed at the cathode?

Write a balanced equation to represent (a) the roasting of nickel(II) sulfide to form nickel(II) oxide. (b) the reduction of nickel(II) oxide by carbon monoxide.

Write a balanced equation to represent the roasting of copper(I) sulfide to form "blister copper"

Write a balanced equation for the reaction that occurs when (a) iron(III) oxide is reduced with carbon monoxide. (b) the excess carbon in pig iron is removed by the basic oxygen process.

Give the formula and name of the compound formed by strontium with (a) nitrogen (b) bromine (c) water (d) oxygen

Give the formula and name of the compound formed by potassium with (a) nitrogen (b) iodine (c) water (d) hydrogen (e) sulfur

Write a balanced equation and give the names of the products for the reaction of (a) magnesium with chlorine. (b) barium peroxide with water. (c) lithium with sulfur. (d) sodium with water.

Write a balanced equation and give the names of the products for the reaction of (a) sodium peroxide and water. (b) calcium and oxygen. (c) rubidium and oxygen. (d) strontium hydride and water.

To inflate a life raft with hydrogen to a volume of \(25.0 \mathrm{~L}\) at \(25^{\circ} \mathrm{C}\) and \(1.10 \mathrm{~atm}\), what mass of calcium hydride must react with water?

What mass of \(\mathrm{KO}_{2}\) is required to remove \(90.0 \%\) of the \(\mathrm{CO}_{2}\) from a sample of \(1.00 \mathrm{~L}\) of exhaled air \(\left(37^{\circ} \mathrm{C}, 1.00 \mathrm{~atm}\right)\) containing \(5.00\) mole percent \(\mathrm{CO}_{2}\) ?

Write a balanced equation to show (a) the reaction of chromate ion with strong acid. (b) the oxidation of water to oxygen gas by permanganate ion in basic solution. (c) the reduction half-reaction of chromate ion to chromium(III) hydroxide in basic solution.

Write a balanced equation to show (a) the formation of gas bubbles when cobalt reacts with hydrochloric acid. (b) the reaction of copper with nitric acid. (c) the reduction half-reaction of dichromate ion to \(\mathrm{Cr}^{3+}\) in acid solution.

Write a balanced redox equation for the reaction of mercury with aqua regia, assuming the products include \(\mathrm{HgCl}_{4^{2-}}\) and \(\mathrm{NO}_{2}(g)\).

Write a balanced redox equation for the reaction of cadmium with aqua regia, assuming the products include \(\mathrm{CdCl}_{4}{\underline{\phantom{xx}}}^{2-}\) and \(\mathrm{NO}(\mathrm{g})\).

Balance the following redox equations. (a) \(\mathrm{Cu}(s)+\mathrm{NO}_{3}^{-}(a q) \longrightarrow \mathrm{Cu}^{2+}(a q)+\mathrm{NO}_{2}(g)\) (acidic) (b) \(\mathrm{Cr}(\mathrm{OH})_{3}(s)+\mathrm{ClO}^{-}(a q) \longrightarrow \mathrm{CrO}_{4}^{2-}(a q)+\mathrm{Cl}^{-}(a q)\) (basic)

Balance the following redox equations. (a) \(\mathrm{Fe}(s)+\mathrm{NO}_{3}^{-}(a q) \longrightarrow \mathrm{Fe}^{3+}(a q)+\mathrm{NO}_{2}(g)\) (acidic) (b) \(\mathrm{Cr}(\mathrm{OH})_{3}(s)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CrO}_{4}^{2-}(a q)\) (basic)

Show by calculation which of the following metals will react with hydrochloric acid (standard concentrations). (a) \(\mathrm{Cd}\) (b) \(\overline{\mathrm{Cr}}\) (c) Co (d) \(\mathrm{Ag}\) (c) Au

Using Table \(20.4\), calculate, for the disproportionation of \(\mathrm{Au}^{+}\), (a) \(K\). (b) the concentration of \(\mathrm{Au}^{+}\) in equilibrium with \(0.10 \mathrm{M} \mathrm{Au}^{3+}\).

A self-contained breathing apparatus contains \(248 \mathrm{~g}\) of potassium superoxide. A firefighter exhales \(116 \mathrm{~L}\) of air at \(37^{\circ} \mathrm{C}\) and \(748 \mathrm{~mm} \mathrm{Hg}\). The volume percent of water in exhaled air is 6.2. What mass of potassium superoxide is left after the water in the exhaled air reacts with it?

Taking \(K_{\text {ip }} \mathrm{PbCl}_{2}=1.7 \times 10^{-5}\) and assuming \(\left[\mathrm{Cl}^{-}\right]=0.20 \mathrm{M}\), calculate the concentration of \(\mathrm{Pb}^{2+}\) at equilibrium.

A \(0.500-\mathrm{g}\) sample of zinc-copper alloy was treated with dilute hydrochloric acid. The hydrogen gas evolved was collected by water displacement at \(27^{\circ} \mathrm{C}\) and a total pressure of \(755 \mathrm{~mm} \mathrm{Hg}\). The volume of the water displaced by the gas is \(105.7 \mathrm{~mL}\). What is the percent composition, by mass, of the alloy? (Vapor pressure of \(\mathrm{H}_{2} \mathrm{O}\) at \(27^{\circ} \mathrm{C}\) is \(26.74 \mathrm{~mm} \mathrm{Hg}\).) Assume only the zinc reacts.

Silver is obtained in much the same manner as gold, using \(\mathrm{NaCN}\) solution and \(\mathrm{O}_{2}\), Describe with appropriate equations the extraction of silver from argentite ore, \(A g_{2}\). . (The products are \(\mathrm{SO}_{2}\) and \(\mathrm{Ag}(\mathrm{CN})_{2}^{-}\), which is reduced with zinc.)

Iron(II) can be oxidized to iron(III) by permanganate ion in acidic solution. The permanganate ion is reduced to manganese(II) ion. (a) Write the oxidation half-reaction, the reduction half-reaction, and the overall redox equation. (b) Calculate \(E^{\circ}\) for the reaction. (c) Calculate the percentage of Fe in an ore if a \(0.3500-\mathrm{g}\) sample is dissolved and the \(\mathrm{Fe}^{2+}\) formed requires for titration \(55.63 \mathrm{~mL}\) of a \(0.0200 \mathrm{M}\) solution of \(\mathrm{KMnO}_{4}\)

Rust, which you can take to be \(\mathrm{Fe}(\mathrm{OH})_{3}\), can be dissolved by treating it with oxalic acid. An acid-base reaction occurs, and a complex ion is formed. (a) Write a balanced equation for the reaction. (b) What volume of \(0.10 \mathrm{M} \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\) would be required to remove a rust stain weighing \(1.0 \mathrm{~g}\) ?

A \(0.500-g\) sample of steel is analyzed for manganese. The sample is dissolved in acid and the manganese is oxidized to permanganate ion. A measured excess of \(\mathrm{Fe}^{2+}\) is added to reduce \(\mathrm{MnO}_{4}^{-}\) to \(\mathrm{Mn}^{2+}\). The excess \(\mathrm{Fe}^{2+}\) is determined by titration with \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{27}\). If \(75.00 \mathrm{~mL}\) of \(0.125 \mathrm{M} \mathrm{FeSO}_{4}\) is added and the excess requires \(13.50 \mathrm{~mL}\) of \(0.100 \mathrm{M} \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) to oxidize \(\mathrm{Fe}^{2+}\), calculate the percent by mass of \(\mathrm{Mn}\) in the sample.

A solution of potassium dichromate is made basic with sodium hydroxide; the color changes from red to yellow. Addition of silver nitrate to the yellow solution gives a precipitate. This precipitate dissolves in concentrated ammonia but re-forms when nitric acid is added. Write balanced net ionic equations for all the reactions in this sequence.