Solved: The electrical conductance of copper metal

Problem 81AP As stated in the chapter, potassium superoxide (KO2) is a useful source of oxygen employed in breathing equipment. Calculate the pressure at which oxygen gas stored at 20°C would have the same density as the oxygen gas provided by KO2. The density of KO2 at 20°C is 2.15 g/cm3.

Problem 1QP Problem Define the terms mineral and ore.

Problem 2QP Problem List three metals that arc usually found in an uncombined state in nature and three metals that are always found in a combined state in nature.

Problem 3QP Problem Write chemical formulas for the following minerals: (a) calcite, (b) dolomite, (c) fluorite, (d) halite, (e) corundum, (f) magnetite, (g) beryl, (h) galena, (i) epsomite, (j) anhydrite.

Problem 4QP Problem Name the following minerals: (a) MgCO3, (b) Na3AlF6, (c) Al2O3, (d) Ag2S, (c) HgS, (f) ZnS, (g) SrSO4, (h) PbCO3, (i) MnO2, ( j) TiO2.

Problem 6QP Problem Describe the main steps involved in the preparation of an ore.

Problem 5QP Problem Define the terms metallurgy, alloy, and amalgam.

What does roasting mean in metallurgy? Why is roasting a major source of air pollution and acid rain?

Problem 8QP Problem Describe with examples the chemical and electrolytic reduction processes used in the production of metals.

Describe the main steps used to purify metals.

Problem 10QP Problem Describe the extraction of iron in a blast furnace.

Problem 11QP Problem Briefly discuss the steelmaking process.

Problem 13QP Problem In the Mond process for the purification of nickel, CO is passed over metallic nickel to give Ni(CO)4: Given that the standard free energies of formation of CO(g) and Ni(CO)4(g) are ?137.3 and ?587.4 kJ/mol, respectively, calculate the equilibrium constant of the reaction at 80°C. (Assume to be independent of temperature.)

Problem 14QP Problem Copper is purified by electrolysis (see Figure 23.6). A 5.00-kg anode is used in a cell where the current is 37.8 A. How long (in hours) must the current run to dissolve this anode and electroplate it onto the cathode?

Problem 15QP Problem Consider the electrolytic procedure for purifying copper described in Figure 23.6. Suppose that a sample of copper contains the following impurities: Fe, Ag, Zn, Au, Co, Pt, and Pb. Which of the metals will be oxidized and dissolved in solution and which will be unaffected and simply form the sludge that accumulates at the bottom of the cell?

Problem 16QP Problem How would you obtain zinc from sphalerite (ZnS)?

Problem 12QP Problem Briefly describe the zone refining process.

Problem 17QP A certain mine produces 2.0 × 108 kg of copper from chalcopyrite (CuFeS2) each year. The ore contains only 0.80 percent Cu by mass. (a) If the density of the ore is 2.8 g/cm3, calculate the volume (in cm3) of ore removed each year, (b) Calculate the mass (in kg) of SO2 produced by roasting (assume chalcopyrite to be the only source of sulfur).

Starting with rutile \(\left(\mathrm{TiO}_2\right)\), explain how you would obtain pure titanium metal. (Hint: First convert \(\mathrm{TiO}_2\) to \(\mathrm{TiCl}_4\). Next, reduce \(\mathrm{TiCl}_4\) with \(\mathrm{Mg}\). Look up physical properties of \(\mathrm{TiCl}_4, \mathrm{Mg}\), and \(\mathrm{MgCl}_2\) in a chemistry handbook.)

Problem 19QP Which of the following compounds would require electrolysis to yield the free metals: Ag2S, CaCl2, NaCl, Fe2O3, Al2O3, TiCl4?

Problem 20QP Although iron is only about two-thirds as abundant as aluminum in Earth’s crust, mass for mass it costs only about one-quarter as much to produce. Why?

Problem 21QP Define the following terms: conductor, insulator, semiconducting elements, donor impurities, acceptor impurities, n-type semiconductors, p-type semiconductors.

Problem 22QP Briefly discuss the nature of bonding in metals, insulators, and semiconducting elements.

State whether silicon would form n-type or p-type semiconductors with the following elements: \(\mathrm{Ga}, \mathrm{Sb}, \mathrm{Al}, \mathrm{As}\).

Problem 25QP Discuss the general properties of metals.

Problem 23QP Describe the general characteristics of n-type and p-type semiconductors.

Problem 26QP Use periodic trends in Ionization energy and electronegativity to show how the metallic character changes within a group.

Problem 28QP How is sodium prepared commercially?

Problem 27QP Use periodic trends in ionization energy and electronegativity to show how the metallic character changes across a period.

Problem 29QP Why is potassium usually not prepared electrolytically from one of its salts?

Problem 30QP Describe the uses of the following compounds: NaCl, Na2CO3, NaOH, KOH, KO2.

Problem 31QP Under what conditions do sodium and potassium form Na? and K- ions?

Problem 32QP Complete and balance the following equations:

Problem 34QP Sodium hydride (NaH) can be used as a drying agent for many organic solvents. Explain how it works.

Problem 33QP Write a balanced equation for each of the following reactions: (a) sodium reacts with water, (b) an aqueous solution of NaOH reacts with CO2, (c) solid Na2CO3, reacts with an HCl solution, (d) solid NaHCO3 reacts with an HCl solution, (e) solid NaHCO3 is heated, (f) solid Na2CO3 is heated.

Problem 35QP Calculate the volume of CO2 at 10.0°C and 746 mmHg pressure obtained by treating 25.0 g of Na2CO3 with an excess of hydrochloric acid.

Problem 37QP How are magnesium and calcium obtained commercially?

Problem 38QP From the thermodynamic data in Appendix 2, calculate the ?Ho values for the following decompositions: Which of the two compounds is more easily decomposed by heat?

Problem 36QP List the common ores of magnesium and calcium.

Problem 40QP Describe two ways of preparing magnesium chloride.

Problem 39QP Starting with magnesium and concentrated nitric acid, describe how you would prepare magnesium oxide. [Hint: First convert Mg to Mg(NO3)2. Next, MgO can be obtained by heating Mg(NO3)2]

The second ionization energy of magnesium is only about twice as great as the first, but the third ionization energy is 10 times as great. Why does it take so much more energy to remove the third electron?

Problem 42QP List the sulfates of the Group 2A metals in order of increasing solubility in water. Explain the trend. (Hint: You need to consult a chemistry handbook.)

Helium contains the same number of electrons in its outer shell as do the alkaline earth metals. Explain why helium is inert whereas the Group \(2 \mathrm{A}\) metals are not.

Problem 45QP Write chemical formulas for (a) quicklime and (b) slaked lime.

Problem 44QP When exposed to air, calcium first forms calcium oxide, which is then converted to calcium hydroxide, and finally to calcium carbonate. Write a balanced equation for each step.

Problem 47QP What action renders aluminum inert?

Problem 46QP Describe the Hall process for preparing aluminum.

Before Hall invented his electrolytic process, aluminum was produced by the reduction of its chloride with an active metal. Which metals would you use for the production of aluminum in that way?

Problem 49QP With the Hall process, how many hours will it take to deposit 664 g of Al at a current of 32.6 A?

Problem 50QP Aluminum forms the complex ions AlCl4 and Describe the shapes of these ions. does not form, Why? (Hint: Consider the relative sizes of Al3+,F+,and Cl? ions.)

Problem 51QP The overall reaction for the electrolytic production of aluminum by means of the Hall process may be represented as At 1000°C, the standard free-energy change for this process is 594 kJ/mol. (a) Calculate the minimum voltage required to produce 1 mole of aluminum at this temperature, (b) If the actual voltage applied is exactly three times the ideal value, calculate the energy required to produce 1.00 kg of the metal.

In basic solution, aluminum metal is a strong reducing agent and is oxidized to \(\mathrm{AlO}_2^{-}\). Give balanced equations for the reaction of \(\mathrm{Al}\) in basic solution with the following: (a) \(\mathrm{NaNO}_3\), to give ammonia; (b) water, to give hydrogen; (c) \(\mathrm{Na}_2 \mathrm{SnO}_3\), to give metallic tin.

Problem 53QP Write a balanced equation for the thermal decomposition of aluminum nitrate to form aluminum oxide, nitrogen dioxide, and oxygen gas.

Problem 54QP Describe some of the properties of aluminum that make it one of the most versatile metals known.

Problem 55QP The pressure of gaseous Al2Cl6 increases more rapidly with temperature than predicted by the ideal gas equation even though Al2Cl6 behaves like an ideal gas. Explain.

Problem 56QP Starting with aluminum, describe with balanced equations how you would prepare (a) Al2Cl6, (b) Al2O3, (e) Al2(SO4)3, (d) NH4Al(SO4)2 · 12H2O.

Problem 57QP Explain the change in bonding when Al2Cl6 dissociates to form AlCl3 in the gas phase.

In steelmaking, nonmetallic impurities such as P, S, and Si are removed as the corresponding oxides. The inside of the furnace is usually lined with \(\mathrm{CaCO}_{3}\) and \(\mathrm{MgCO}_{3}\), which decompose at high temperatures to yield CaO and MgO. How do CaO and MgO help in the removal of the nonmetallic oxides?

Problem 59AP When 1. 164 g of a certain metal sulfide was roasted in air, 0.972 g of the metal oxide was formed. If the oxidation number of the metal is +2, calculate the molar mass of the metal.

Problem 60AP An early view of metallic bonding assumed that bonding in metals consisted of localized, shared electron-pair bonds between metal atoms. What evidence would help you to argue against this viewpoint?

Problem 61AP Referring to Figure 23.6, would you expect H2O and H to be reduced at the cathode and H2O oxidized at the anode?

Problem 62AP A 0.450-g sample of steel contains manganese as an impurity. The sample is dissolved in acidic solution and the manganese is oxidized to the permanganate ion The ion is reduced to Mn2+ by reacting with 50.0 mL of 0.0800 M FeSO4 solution.The excess Fe2+ ions are then oxidized to Fe3+ by 22.4 mL of 0.0100 M K2Cr2O7.Calculate the percent by mass of manganese in the sample.

Problem 63AP Given that and that calculate ?Go for the following reactions at 25°C:

Problem 64AP Use compounds of aluminum as examples to explain what is meant by amphoterism.

Problem 65AP When an inert atmosphere is needed for a metallurgical process, nitrogen is frequently used. However, in the reduction of TiCl4 by magnesium, helium is used. Explain why nitrogen is not suitable for this process.

It has been shown that \(\mathrm{Na}_{2}\) species form in the vapor phase. Describe the formation of the “disodium molecule” in terms of a molecular orbital energy level diagram. Would you expect the alkaline earth metals to exhibit a similar property?

Problem 67AP Explain each of the following statements: (a) An aqueous solution of AlCl3 is acidic, (b) Al(OH)3 is soluble in NaOH solution but not in NH3 solution.

Problem 68AP Write balanced equations for the following reactions: (a) the heating of aluminum carbonate, (b) the reaction between AlCl3 and K, (c) the reaction between solutions of Na2CO3 and Ca(OH)2.

Problem 69AP Write a balanced equation for the reaction between calcium oxide and dilute HCl solution.

Problem 71AP Explain why most metals have a flickering appearance.

Problem 70AP What is wrong with the following procedure for obtaining magnesium?

Problem 72AP Predict the chemical properties of francium, the last member of Group 1 A.

Problem 73AP Describe a medicinal or health-related application for each of the following compounds: NaF, Li2CO3, Mg(OH)2, CaCO3, BaSO4.

Problem 74AP The following are two reaction schemes involving magnesium. Scheme 1: When magnesium bums in oxygen, a white solid (A) is formed. A dissolves in 1 M HCl to give a colorless solution (B). Upon addition of Na2CO3 to B, a white precipitate is formed (C). On heating, C decomposes to D and a colorless gas is generated (E). When E is passed through limewater [an aqueous suspension of Ca(OH)2], a white precipitate appears (F). Scheme II: Magnesium reacts with 1 M H2SO4 to produce a colorless solution (G). Treating G with an excess of NaOH produces a white precipitate (H). H dissolves in 1 M HNO3 to form a colorless solution. When the solution is slowly evaporated, a white solid (I) appears. On heating I, a brown gas is given off. Identify A?I, and write equations representing the reactions involved.

Problem 75AP Lithium and magnesium exhibit a diagonal relationship in some chemical properties. How does lithium resemble magnesium in its reaction with oxygen and nitrogen? Consult a handbook of chemistry and compare the solubilities of carbonates, fluorides, and phosphates of these metals.

To prevent the formation of oxides, peroxides, and superoxides, alkali metals are sometimes stored in an inert atmosphere. Which of the following gasses should not be used for lithium: Ne, Ar, \(\mathrm{N}_{2}\), Kr? Why?

Problem 77AP Which of the following metals is not found in the free state in nature: Ag, Cu, Zn, Au, Pt?

Problem 78AP After heating, a metal surface (such as that of a cooking pan or skillet) develops a color pattern like an oil slick on water. Explain.

Problem 79AP A sample of 10.00 g of sodium reacts with oxygen to form 13.83 g of sodium oxide (Na2O) and sodium peroxide (Na2O2). Calculate the percent composition of the mixture.

The electrical conductance of copper metal decreases with temperature, but that of a \(\mathrm{CuSO}_{4}\) solution increases with temperature. Explain.

Problem 82AP Problem Chemical tests of four metals A, B, C, and D show the following results: (a) Only B and C react with 0.5 M HCl to give H2 gas. (b) When B is added to a solution containing the ions of the other metals, metallic A, C, and D are formed, (c) A reacts with 6 M HNO3, but D does not. Arrange the metals in the increasing order as reducing agents Suggest four metals that fit these descriptions.