A voltaic cell utilizes the following reaction: 4 Fe2+1aq2 + O21g2 + 4 H+1aq2 ¡ 4 Fe3+1aq2 + 2 H2O1l2 (a) What is the emf of this cell under standard conditions?

A voltaic cell utilizes the following reaction: 4 Fe2+1aq2 + O21g2 + 4 H+1aq2 ¡ 4 Fe3+1aq2 + 2 H2O1l2 (b) What is the emf of this cell when 3Fe2+4 = 1.3 M, 3Fe3+4= 0.010 M, PO2 = 0.50 atm, and the pH of the solution in the cathode half-cell is 3.50?

A voltaic cell utilizes the following reaction: 2 Fe3+1aq2 + H21g2 ¡ 2 Fe2+1aq2 + 2 H+1aq2 (a) What is the emf of this cell under standard conditions?

A voltaic cell utilizes the following reaction: (b) What is the emf for this cell when 3Fe3+4 = 3.50 M, PH2= 0.95 atm, 3Fe2+4 = 0.0010 M, and the pH in both half-cells is 4.00?

A voltaic cell is constructed that is based on the following reaction: Sn²⁺(aq) + Pb(s) → Sn(s) + Pb²⁺(aq) (a) If the concentration of Sn²⁺ in the cathode half-cell is 1.00 M and the cell generates an emf of +0.22 V, what is the concentration of Pb²⁺ in the anode half-cell?

During a period of discharge of a lead–acid battery, 402 g of Pb from the anode is converted into PbSO₄(s). (a) What mass of PbO₂(s) is reduced at the cathode during this same period?

During a period of discharge of a lead–acid battery, 402 g of Pb from the anode is converted into PbSO₄(s). (b) How many coulombs of electrical charge are transferred from Pb to PbO₂?

During the discharge of an alkaline battery, 4.50 g of Zn is consumed at the anode of the battery. (b) How many coulombs of electrical charge are transferred from Zn to MnO₂?

Heart pacemakers are often powered by lithium–silver chromate 'button' batteries. The overall cell reaction is 2 Li(s) + Ag₂CrO₄(s) → Li₂CrO₄(s) + 2 Ag(s) (a) Lithium metal is the reactant at one of the electrodes of the battery. Is it the anode or the cathode?

Heart pacemakers are often powered by lithium–silver chromate 'button' batteries. The overall cell reaction is 2 Li(s) + Ag₂CrO₄(s) → Li₂CrO₄(s) + 2 Ag(s) (b) Choose the two half-reactions from Appendix E that most closely approximate the reactions that occur in the battery. What standard emf would be generated by a voltaic cell based on these half-reactions?

In some applications nickel–cadmium batteries have been replaced by nickel–zinc batteries. The overall cell reaction for this relatively new battery is: 2 H₂O(l) + 2 NiO(OH)(s) + Zn(s) → 2 Ni(OH)₂(s) + Zn(OH)₂(s) (b) What is the anode half-reaction?

In some applications nickel–cadmium batteries have been replaced by nickel–zinc batteries. The overall cell reaction for this relatively new battery is: 2 H₂O(l) + 2 NiO(OH)(s) + Zn(s) → 2 Ni(OH)₂(s) + Zn(OH)₂(s) (c) A single nickel–cadmium cell has a voltage of 1.30 V. Based on the difference in the standard reduction potentials of Cd²⁺ and Zn²⁺, what voltage would you estimate a nickel–zinc battery will produce? (d) Would you expect the specific energy density of a nickel–zinc battery to be higher or lower than that of a nickel–cadmium battery?

Li-ion batteries used in automobiles typically use a LiMn2O4 cathode in place of the LiCoO2 cathode found in most Li-ion batteries. (a) Calculate the mass percent lithium in each electrode material.

Li-ion batteries used in automobiles typically use a LiMn2O4 cathode in place of the LiCoO2 cathode found in most Li-ion batteries. (b) Which material has a higher percentage of lithium? Does this help to explain why batteries made with LiMn2O4 cathodes deliver less power on discharging?

Li-ion batteries used in automobiles typically use a LiMn2O4 cathode in place of the LiCoO2 cathode found in most Li-ion batteries. (c) In a battery that uses a LiCoO2 cathode, approximately 50% of the lithium migrates from the cathode to the anode on charging. In a battery that uses a LiMn2O4 cathode, what fraction of the lithium in LiMn2O4 would need to migrate out of the cathode to deliver the same amount of lithium to the graphite anode?

(a) Which reaction is spontaneous in the hydrogen fuel cell: hydrogen gas plus oxygen gas makes water, or water makes hydrogen gas plus oxygen gas?

(b) Using the standard reduction potentials in Appendix E, calculate the standard voltage generated by the hydrogen fuel cell in acidic solution.

(b) Can the “fuel” of a fuel cell be a solid?

Iron corrodes to produce rust, Fe₂O₃, but other corrosion products that can form are Fe(O)(OH), iron oxyhydroxide, and magnetite, Fe₃O₄. (a) What is the oxidation number of Fe in iron oxyhydroxide, assuming oxygen's oxidation number is -2? (b) The oxidation number for Fe in magnetite was controversial for a long time. If we assume that oxygen’s oxidation number is - 2, and Fe has a unique oxidation number, what is the oxidation number for Fe in magnetite? (O)(OH), iron oxyhydroxide, and magnetite, Fe₃O₄. (c) It turns out that there are two different kinds of Fe in magnetite that have different oxidation numbers. Suggest what these oxidation numbers are and what their relative stoichiometry must be, assuming oxygen’s oxidation number is -2.

Copper corrodes to cuprous oxide, Cu2O, or cupric oxide, CuO, depending on environmental conditions. (a) What is the oxidation state of copper in cuprous oxide?

(c) What process occurs at the anode in the electrolysis of molten NaCl?

(d) Why is sodium metal not obtained when an aqueous solution of NaCl undergoes electrolysis?

(d) Why are active metals such as Al obtained by electrolysis using molten salts rather than aqueous solutions?

(a) A Cr³⁺(aq) solution is electrolyzed, using a current of 7.60 A. What mass of Cr(s) is plated out after 2.00 days?

(b) What amperage is required to plate out 0.250 mol Cr from a Cr³⁺ solution in a period of 8.00 h?

(a) Calculate the mass of Li formed by electrolysis of molten LiCl by a current of 7.5 × 10⁴ A flowing for a period of 24 h. Assume the electrolytic cell is 85% efficient. (b) What is the minimum voltage required to drive the reaction?