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- (b) Given the following reduction potentials, calculate the standard emf of the cell: Cd1OH221s2 + 2 e- ¡ Cd1s2 + 2 OH-1aq2 E°red = -0.76 V NiO1OH21s2 + H2O1l2 + e- ¡ Ni1OH221s2 + OH-1aq2 E°red = +0.49 V
Problem 104
- The capacity of batteries such as the typical AA alkaline battery is expressed in units of milliamp-hours (mAh). An AA alkaline battery yields a nominal capacity of 2850 mAh. (a) What quantity of interest to the consumer is being expressed by the units of mAh?
Problem 105
Problem 105b
The capacity of batteries such as the typical AA alkaline battery is expressed in units of milliamp-hours (mAh). An AA alkaline battery yields a nominal capacity of 2850 mAh. (b) The starting voltage of a fresh alkaline battery is 1.55 V. The voltage decreases during discharge and is 0.80 V when the battery has delivered its rated capacity. If we assume that the voltage declines linearly as current is withdrawn, estimate the total maximum electrical work the battery could perform during discharge.
- If you wanted to convert a disulfide to two thiols, should you add a reducing agent or an oxidizing agent to the solution?
Problem 106
Problem 106b
Disulfides are compounds that have S ¬ S bonds, like peroxides have O ¬ O bonds. Thiols are organic compounds that have the general formula R ¬ SH, where R is a generic hydrocarbon. The SH- ion is the sulfur counterpart of hydroxide, OH-. Two thiols can react to make a disulfide, R ¬ S ¬ S ¬ R. (b) What is the oxidation state of sulfur in a disulfide?
Problem 106c
Disulfides are compounds that have S ¬ S bonds, like peroxides have O ¬ O bonds. Thiols are organic compounds that have the general formula R ¬ SH, where R is a generic hydrocarbon. The SH- ion is the sulfur counterpart of hydroxide, OH-. Two thiols can react to make a disulfide, R ¬ S ¬ S ¬ R. (c) If you react two thiols to make a disulfide, are you oxidizing or reducing the thiols?
- (a) How many coulombs are required to plate a layer of chromium metal 0.25 mm thick on an auto bumper with a total area of 0.32 m² from a solution containing CrO₄²⁻? The density of chromium metal is 7.20 g/cm³. (b) What current flow is required for this electroplating if the bumper is to be plated in 10.0 s? (c) If the external source has an emf of +6.0 V and the electrolytic cell is 65% efficient, how much electrical power is expended to electroplate the bumper?
Problem 107
- Magnesium is obtained by electrolysis of molten MgCl2. (b) Several cells are connected in parallel by very large copper bars that convey current to the cells. Assuming that the cells are 96% efficient in producing the desired products in electrolysis, what mass of Mg is formed by passing a current of 97,000 A for a period of 24 h?
Problem 108
Problem 109
Calculate the number of kilowatt-hours of electricity required to produce 1.0 * 103 kg (1 metric ton) of aluminum by electrolysis of Al3+ if the applied voltage is 4.50 V and the process is 45% efficient.
- The Haber process is the principal industrial route for converting nitrogen into ammonia: N2(g) + 3 H2(g) → 2 NH3(g). (c) Calculate the standard emf of the Haber process at room temperature.
Problem 111
Problem 111b
The Haber process is the principal industrial route for converting nitrogen into ammonia: N2(g) + 3 H2(g) → 2 NH3(g) (b) Using the thermodynamic data in Appendix C, calculate the equilibrium constant for the process at room temperature.
- In a galvanic cell, the cathode is an Ag+ | 1.00 M | Ag(s) half-cell. The anode is a standard hydrogen electrode immersed in a buffer solution containing 0.10 M benzoic acid (C6H5COOH) and 0.050 M sodium benzoate (C6H5COO-Na+). The measured cell voltage is 1.030 V. What is the pKa of benzoic acid?
Problem 112
Problem 113a,b,d
Aqueous solutions of ammonia (NH3) and bleach (active ingredient NaOCl) are sold as cleaning fluids, but bottles of both of them warn: 'Never mix ammonia and bleach, as toxic gases may be produced.' One of the toxic gases that can be produced is chloroamine, NH2Cl. (a) What is the oxidation number of chlorine in bleach? (active ingredient NaOCl) are sold as cleaning fluids, but bottles of both of them warn: “Never mix ammonia and bleach, as toxic gases may be produced.” One of the toxic gases that can be produced is chloroamine, NH2Cl. (b) What is the oxidation number of chlorine in chloramine? (d) Another toxic gas that can be produced is nitrogen trichloride, NCl3. What is the oxidation number of N in nitrogen trichloride?
Problem 113e
Aqueous solutions of ammonia 1NH32 and bleach (active ingredient NaOCl) are sold as cleaning fluids, but bottles of both of them warn: 'Never mix ammonia and bleach, as toxic gases may be produced.' One of the toxic gases that can be produced is chloroamine, NH2Cl. (e) Is N oxidized, reduced, or neither, upon the conversion of ammonia to nitrogen trichloride?
- A voltaic cell is based on Ag+ (aq) > Ag (s) and Fe3+ (aq) > Fe2+ (aq) half-cells. Use S° values in Appendix C and the relationship between cell potential and free-energy change to predict whether the standard cell potential increases or decreases when the temperature is raised above 25 °C.
Problem 114
- Hydrogen gas has the potential for use as a clean fuel in reaction with oxygen. The relevant reaction is 2 H2(g) + O2(g) → 2 H2O(l). Consider two possible ways of utilizing this reaction as an electrical energy source: (i) Hydrogen and oxygen gases are combusted and used to drive a generator, much as coal is currently used in the electric power industry; (ii) hydrogen and oxygen gases are used to generate electricity directly by using fuel cells that operate at 85 °C. Based on the analysis here, would it be more efficient to use the combustion method or the fuel-cell method to generate electrical energy from hydrogen?
Problem 115
Problem 116
Cytochrome, a complicated molecule that we will represent as CyFe2+, reacts with the air we breathe to supply energy required to synthesize adenosine triphosphate (ATP). The body uses ATP as an energy source to drive other reactions (Section 19.7). At pH 7.0 the following reduction potentials pertain to this oxidation of CyFe2+: O21g2 + 4 H+1aq2 + 4 e- ¡ 2 H2O1l2 Ered ° = +0.82 V CyFe3+1aq2 + e- ¡ CyFe2+1aq2 E°red = +0.22 V (a) What is ∆G for the oxidation of CyFe2+ by air? (b) If the synthesis of 1.00 mol of ATP from adenosine diphosphate (ADP) requires a ∆G of 37.7 kJ, how many moles of ATP are synthesized per mole of O2?
Problem 116b
Cytochrome, a complicated molecule that we will represent as CyFe2+, reacts with the air we breathe to supply energy required to synthesize adenosine triphosphate (ATP). The body uses ATP as an energy source to drive other reactions (Section 19.7). At pH 7.0 the following reduction potentials pertain to this oxidation of CyFe2+: O21g2 + 4 H+1aq2 + 4 e- ¡ 2 H2O1l2 Ered ° = +0.8 (b) If the synthesis of 1.00 mol of ATP from adenosine diphosphate (ADP) requires a ∆G of 37.7 kJ, how many moles of ATP are synthesized per mole of O2?
- The standard potential for the reduction of AgSCN(s) is +0.09 V. AgSCN(s) + e⁻ → Ag(s) + SCN⁻(aq). Using this value and the electrode potential for Ag⁺(aq), calculate the Ksp for AgSCN.
Problem 117
- The Ksp value for PbS(s) is 8.0 * 10^-28. By using this value together with an electrode potential from Appendix E, determine the value of the standard reduction potential for the reaction PbS(s) + 2 e^- → Pb(s) + S^2-(aq).
Problem 118
Problem 119
A student designs an ammeter (a device that measures electrical current) that is based on the electrolysis of water into hydrogen and oxygen gases. When electrical current of unknown magnitude is run through the device for 2.00 min, 12.3 mL of water-saturated H21g2 is collected. The temperature of the system is 25.5 °C, and the atmospheric pressure is 768 torr. What is the magnitude of the current in amperes?