Ch.18 - ElectrochemistryWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

In voltaic/galvanic cells electrical current is created, while in an electrolytic cell electrical current is consumed to drive the reaction. 

The Ampere

The ampere or amp represents the SI unit for electrical current and represents charge per second. 

Example #1: Gold can be plated out of a solution containing Au3+ based on the following half reaction:

Au3+ (aq) + 3 e -  ---->  Au (s)

a) What mass of gold is plated by a 41 minute flow of 6.8 A current?

Example #2: A solution of Mn+5 is used to plate out Mn in an electrochemical cell. If a total of 1.13 g of Mn is plated out in a total time of 1600 seconds, what was the electrical current used? (MW of Mn is 54.94 g/mol)

Example #3: If steady current of 15 amperes is provided by a stable voltage of 12 Volts for 600 seconds, answer each of the following questions.

a)  Calculate the total charge that passes through the circuit in this time.

b)  Calculate the total number of moles of electrons that pass through the circuit in this time.

c)  Calculate the total amount of energy that passes through the circuit in this time.

d)  Calculate the power that the battery provides during this process.

 

 

Additional Problems
A current of 5.00 A is passed through an aqueous solution of chromium (III) nitrate for 30.0 min. How many grams of chromium metal will be deposited at the cathode? a) 0.027 g b) 1.62 g c) 4.85 g d) 6.33 g
What mass of lead sulfate is formed in a lead-acid storage battery when 1.00 g of Pb undergoes oxidation?
Copper can be electroplated at the cathode of an electrolysis cell by the half-reaction: Cu2+(aq) + 2 e– → Cu(s) How much time would it take for 325 mg of copper to be plated at a current of 5.6 A?
Silver can be electroplated at the cathode of an electrolysis cell by the half-reaction: Ag+ (aq) + e– → Ag (s) What mass of silver would plate onto the cathode if a current of 6.8 A flowed through the cell for 72 min?
A major source of sodium metal is the electrolysis of molten sodium chloride. What magnitude of current produces 1.0 kg of sodium metal in 1 hour?
What mass of aluminum metal can be produced per hour in the electrolysis of a molten aluminum salt by a current of 25 A?
Determine if HNO3 can dissolve each metal sample. If it can, write a balanced chemical reaction showing how the metal dissolves in HNO3 and determine the minimum volume of 6.0 M HNO3 required to completely dissolve the sample. a. 5.90 g Au b. 2.55 g Cu c. 4.83 g Sn
The molar mass of a metal (M) is 50.9 g/mol; it forms a chloride of unknown composition. Electrolysis of a sample of the molten chloride with a current of 6.42 A for 23.6 minutes produces 1.20 g of M at the cathode. Determine the empirical formula of the chloride.
A 0.0251 L sample of a solution of Cu + requires 0.0322 L of 0.129 M KMnO4 solution to reach the equivalence point. The products of the reaction are Cu2+ and Mn2+. What is the concentration of the Cu2+ solution?
A current of 11.3 A is applied to 1.25 L of a solution of 0.552 M HBr converting some of the H+ to H2(g), which bubbles out of solution. What is the pH of the solution after 73 minutes?
A 215 mL sample of a 0.500 M NaCl solution with an initial pH of 7.00 is subjected to electrolysis. After 15.0 minutes, a 10.0 mL portion (or aliquot) of the solution was removed from the cell and titrated with 0.100 M HCI solution. The endpoint in the titration was reached upon addition of 22.8 mL of HCl. Assuming constant current, what was the current (in A) running through the cell?
Amps are equivalent to which unit? A.  Volts B.  Moles of e− C.  Coulombs D.  Volts / second E.  Coulombs / second  
If the following half-reactions are used in an electrolytic cell:             Li+(aq) + e − → Li(s)                E° = −3.04             Mg2+(aq) + 2 e − → Mg(s)       E° = −2.38 And 10 Amps are applied for 1 minute, determine which solid would form and how much would form in grams. A.  0.043 grams of Lithium B.  0.022 grams of Lithium C.  0.15 grams of Magnesium D.  0.076 grams of Magnesium E.  0.086 grams of Lithium  
Gold can be plated out of a solution containing Au 3+ based on the following half reaction: Au 3+ (aq) + 3 e -      →       Au (s)   What mass of gold is plated by a 53 minute flow of 8.2 A current?
A solution of Mn+5 is used to plate out Mn in an electrochemical cell. If a total of 3.70 g of Mn is plated out in a total time of 1 seconds, what was the electrical current used? (MW of Mn is 54.94 g/mol)  
The following half-reactions combine to make an electrolytic cell: K+ (aq) + e- → K (s)                                       E° = −2.93 Li+ (aq) + e- → Li (s)                                      E° = −3.05 If a current of 1.5 Amps is placed on this cell for 5 minutes, which of the following describes the mass of solid formed (in grams) and the voltage required of the current. [1 Amp = 1 coul/s;    96500 coul = 1 mol e-] A.  0.0324 g;  - 0.12 V             B. 0.000539 g ; - 0.12 V                      C. 0.00466 g;  0.12 V                    D. 0.0324 g;  5.98 V                           E.  0.00466 g;  5.98 V  
How many seconds will be required to deposit 6.23 g of Ag from a solution that contains Ag+ ions if a current of 0.35 A is used? a. 1.7 x 106 b. 1.6 x 104 c. 2.0 x 103 d. 2.1 x 102
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 2.10 min , 12.1 mL of water-saturated H2 (g) is collected. The temperature of the system is 25.5 oC, and the atmospheric pressure is 761 torr .What is the magnitude of the current in amperes?
In a Li-ion battery the composition of the cathode is LiCoO2 when completely discharged. On charging approximately 50% of the Li + ions can be extracted from the cathode and transported to the graphite anode where they intercalate between the layers.If the LiCoO2 cathode has a mass of 21 g (when fully discharged), how many coulombs of electricity can be delivered on completely discharging a fully charged battery?
During a period of discharge of a lead-acid battery, 406 g of Pb from the anode is converted into PbSO4 (s).What mass of PbO2 (s) is reduced at the cathode during this same period?
A vanadium electrode is oxidized electrically. If the mass of the electrode decreases by 114 mg during the passage of 650 coulombs, what is the oxidation state of the vanadium product?a) +1b) +2c) +3d) +4
Determine the optimum mass ratio of Zn to MnO 2 in an alkaline battery.
A given amount of electric charge deposits 2.159 g of silver from an Ag + solution. What mass of copper from a Cu2+ solution will be deposited by the same amount of electric charge?A. 0.635 gB. 1.97 gC. 2.54 gD. 127 g
If each of these ions were reduced to metal with one coulomb, which would yield the greatest mass?A. Cu2+B. Ag+C. Hg2+D. Cu+
A battery relies on the oxidation of magnesium and the reduction of Cu 2+. The initial concentrations of Mg2+ and Cu2+ are 1.0 x 10–4 M and 1.5 M, respectively, in 1.0-liter half-cells.b. What is the voltage of the battery after delivering 5.0 A for 8.0 h?
A battery relies on the oxidation of magnesium and the reduction of Cu 2+. The initial concentrations of Mg2+ and Cu2+ are 1.0 x 10–4 M and 1.5 M, respectively, in 1.0-liter half-cells.c. How long can the battery deliver 5.0 A before going dead?
A rechargeable battery is constructed based on a concentration cell constructed of two Ag/Ag+ half-cells. The volume of each half-cell is 2.0 L and the concentrations of Ag + in the half-cells are 1.25 M and 1.0 x 10–3 M.a. How long can this battery deliver 2.5 A of current before it goes dead?
A rechargeable battery is constructed based on a concentration cell constructed of two Ag/Ag+ half-cells. The volume of each half-cell is 2.0 L and the concentrations of Ag + in the half-cells are 1.25 M and 1.0 x 10–3 M.c. Upon recharging, how long would it take to redissolve 1.00 x 10 2 g of silver at a charging current of 10.0 amps?
How many minutes will be required to deposit 1.00 g of chromium metal from an aqueous CrO42- solution using a current of 6.00 amperes?(A) 186 min(B) 30.9 min(C) 15.4 min(D) 5.15 min
If the following half-reactions are used in an electrolytic cell:Li +(aq) +  e−  →  Li(s)          E  0 = − 3.04Mg 2+(aq) + 2e−  →  Mg(s)   E 0 = − 2.38And 10 Amps are applied for 1 minute, determine which solid would form and how much would form in grams. A. 0.043 grams of LithiumB. 0.022 grams of LithiumC. 0.15 grams of MagnesiumD. 0.076 grams of MagnesiumE. 0.086 grams of Lithium  
A single Hall–Heroult cell (as shown in Figure below ) produces about 1 ton of aluminum in 24 h. What current must be used to accomplish this?
One of the few industrial-scale processes that produce organic compounds electrochemically is used by the Monsanto Company to produce 1,4-dicyanobutane. The reduction reaction is 2CH2=CHCN + 2H+ + 2e- → NC—(CH2)4—CN The NC—(CH2)4—CN is then chemically reduced using hydrogen gas to H2N—(CH2)6—NH2, which is used in the production of nylon. What current must be used to produce 150. kg NC—(CH2)4—CN per hour?
Even though the toxicity of cadmium has become a concern, nickel-cadmium (nicad) batteries are still used commonly in many devices. The overall cell reaction isCd(s) + 2NiO(OH)(s) + 2H 2O(l) ⟶ 2Ni(OH)(s) + Cd(OH)2(s)A certain nicad battery weighs 18.3 g and has a capacity of 300. mA⋅h (that is, the cell can store charge equivalent to a current of 300. mA flowing for 1 h).(a) What is the capacity of this cell in coulombs?
Assume that you want to construct a voltaic cell that uses the following half reactions:A2 +  ( aq ) + 2e-  →  A( s )Eredo= -0.13VB2 +  ( aq ) + 2e-  →  B( s )Eredo= -1.12VYou begin with the incomplete cell pictured below, in which the electrodes are immersed in water.What voltage will the cell generate under standard conditions?
During a period of discharge of a lead-acid battery, 402 g of Pb from the anode is converted into PbSO4 (s).How many coulombs of electrical charge are transferred from Pb to PbO2?
During the discharge of an alkaline battery, 4.60 g of Zn are consumed at the anode of the battery.How many coulombs of electrical charge are transferred from Zn to MnO2?
Some years ago a unique proposal was made to raise the Titanic. The plan involved placing pontoons within the ship using a surface-controlled submarine-type vessel. The pontoons would contain cathodes and would be filled with hydrogen gas formed by the electrolysis of water. It has been estimated that it would require about 7 x 108 mol of H2 to provide the buoyancy to lift the ship (J. Chem. Educ., Vol. 50, 1973, 61). Assume that pH of the seawater is 7 and temperature of the seawater is 25oC.How many coulombs of electrical charge would be required?
Some years ago a unique proposal was made to raise the Titanic. The plan involved placing pontoons within the ship using a surface-controlled submarine-type vessel. The pontoons would contain cathodes and would be filled with hydrogen gas formed by the electrolysis of water. It has been estimated that it would require about 7 x 108 mol of H2 to provide the buoyancy to lift the ship (J. Chem. Educ., Vol. 50, 1973, 61). Assume that pH of the seawater is 7 and temperature of the seawater is 25oC.What is the minimum voltage required to generate H2 and O2 if the pressure on the gases at the depth of the wreckage (2 mi) is 300 atm?
Some years ago a unique proposal was made to raise the Titanic. The plan involved placing pontoons within the ship using a surface-controlled submarine-type vessel. The pontoons would contain cathodes and would be filled with hydrogen gas formed by the electrolysis of water. It has been estimated that it would require about 7 x 108 mol of H2 to provide the buoyancy to lift the ship (J. Chem. Educ., Vol. 50, 1973, 61). Assume that pH of the seawater is 7 and temperature of the seawater is 25oC.What is the minimum cost of the electrical energy required to generate the necessary H2 if the electricity costs 83 cents per kilowatt-hour to generate at the site?
If a 2.5 A current is run through a circuit for 35 minutes, how many coulombs of charge moved through the circuit?
A 216 mL sample of a 0.500 M NaCl solution with an initial pH of 7.00 is subjected to electrolysis. After 15 minutes, a 10.0-mL portion (or aliquot) of the solution was removed from the cell and titrated with 0.100 M HCl solution. The endpoint in the titration was reached upon addition of 22.7 mL of HCl. Assuming constant current, what was the current (in A) running through the cell?
Calculate the number of kilowatt-hours of electricity required to produce 1.0 x 103 kg (1 metric ton) of aluminum by electrolysis of Al3+ if the applied voltage is 4.60 V and the process is 46 % efficient.
The overall cell reaction occurring in an alkaline battery isZn(s) + MnO2(s) + H2O(l) ⟶ ZnO(s) + Mn(OH)2(s)(b) If 4.50 g of zinc is oxidized, how many grams of manganese dioxide and of water are consumed?(d) How many coulombs are produced in part (b)?
An inexpensive and accurate method of measuring the quantity of electricity flowing through a circuit is to pass the current through a solution of a metal ion and weigh the metal deposited. A silver electrode immersed in an Ag+ solution weighs 1.7854 g before the current has passed and weighs 1.8016 g after the current has passed. How many coulombs have passed?
An aqueous solution of PdCl 2 is electrolyzed for 48.6 seconds, and during this time 0.1064 g of Pd is deposited on the cathode. What is the average current used in the electrolysis?
Commercial electrolytic cells for producing aluminum operate at 5.0 V and 100,000 A.(a) How long does it take to produce exactly 1 metric ton (1000 kg) of aluminum?(b) How much electrical power (in kilowatt-hours, kW·h) is used (1 W = 1 J/s; 1 kW·h = 3.6 × 10  3 kJ)?
Commercial electrolytic cells for producing aluminum operate at 5.0 V and 100,000 A.(c) If electricity costs $0.123 per kW·h and cell efficiency is 90.%, what is the cost of electricity to produce exactly 1 lb of aluminum?
Magnesium bars are connected electrically to underground iron pipes to serve as sacrificial anodes.(b) A 12-kg Mg bar is attached to an iron pipe, and it takes 8.5 yr for the Mg to be consumed. What is the average current flowing between the Mg and the Fe during this period?
Copper can be electroplated at the cathode of an electrolysis cell by the half-reaction: Cu2+(aq) + 2 e– → Cu(s)How much time would it take for 326 mg of copper to be plated at a current of 6.1 A?
How long would it take to reduce 1 mole of the following ion using the current indicated? Assume the voltage is sufficient to perform the reduction.(a) Al3+, 1.234 A
How long would it take to reduce 1 mole of the following ion using the current indicated? Assume the voltage is sufficient to perform the reduction.(b) Ca2+, 22.2 A
How long would it take to reduce 1 mole of the following ion using the current indicated? Assume the voltage is sufficient to perform the reduction.(c) Cr5+, 37.45 A
How long would it take to reduce 1 mole of the following ion using the current indicated? Assume the voltage is sufficient to perform the reduction.(d) Au3+, 3.57 A
A battery is constructed based on the oxidation of magnesium and the reduction of Cu2+. The initial concentrations of Mg2+ and Cu2+ are 1.2×10−4 M and 1.6 M, respectively, in 1.0-liter half-cells. What is the voltage of the battery after delivering 4.9 A for 8.0 h?
A battery is constructed based on the oxidation of magnesium and the reduction of Cu2+. The initial concentrations of Mg2+ and Cu2+ are 1.2×10−4 M and 1.6 M, respectively, in 1.0-liter half-cells. How long can the battery deliver 4.9 A before going dead?
A rechargeable battery is constructed based on a concentration cell constructed of two Ag/Ag+ half-cells. The volume of each half-cell is 2.1 L and the concentrations of Ag+ in the half-cells are 1.30 M and 1.2×10−3 M. For how long can this battery deliver 2.6 A of current before it goes dead?
A rechargeable battery is constructed based on a concentration cell constructed of two Ag/Ag+ half-cells. The volume of each half-cell is 2.1 L and the concentrations of Ag+ in the half-cells are 1.30 M and 1.2×10−3 M. Upon recharging, how long would it take to redissolve 120 g of silver at a charging current of 10.0 amps?
A thin layer of gold can be applied to another material by an electrolytic process. The surface area of an object to be gold plated is 49.7 cm2 and the density of gold is 19.3/cm3. A current of 3.30 A is applied to a solution that contains gold in the +3 oxidation state. Calculate the time required to deposit an even layer of gold 1.20×10−3 cm thick on the object.
Three electrolytic cells are connected in a series. The electrolytes in the cells are aqueous copper(II) sulfate, gold(III) sulfate, and silver nitrate. A current of 2.36 A is applied and after some time 1.74 g Cu is deposited. How long was the current applied?
Silver can be plated out of a solution containing Ag+ according to the half-reaction: Ag+(aq) + e– →  Ag(s)How much time (in minutes) does it take to plate 16 g of silver using a current of 3.6 A?
Copper is plated onto the cathode of an electrolytic cell containing CuCl2(aq). How long does it take to plate 126 mg of copper with a current of 3.6 A?
How much time is needed to deposit 1.0 g of chromium metal from an aqueous solution of CrCl3 using a current of 1.5 A?
How many seconds does it take to deposit 65.5 g of Zn on a steel gate when 21.0 A is passed through a ZnSO4 solution?
How many seconds does it take to deposit 1.63 g of Ni on a decorative drawer handle when 13.7 A is passed through a Ni(NO3)2 solution?
The MnO2 used in alkaline batteries can be produced by an electrochemical process of which one half-reaction isMn2+(aq) + 2H2O(l) ⟶ MnO2(s) + 4H+(aq) + 2e−If a current of 25.0 A is used, how many hours are needed to produce 1.00 kg of MnO  2? At which electrode is the MnO2 formed?
(a) How many minutes does it take to form 10.0 L of O 2 measured at 99.8 kPa and 28°C from water if a current of 1.3 A passes through the electrolytic cell?
(a) How many minutes does it take to form 10.0 L of O 2 measured at 99.8 kPa and 28°C from water if a current of 1.3 A passes through the electrolytic cell?(b) What mass of H2 forms?
A silver button battery used in a watch contains 0.75 g of zinc and can run until 80% of the zinc is consumed.(a) For how many days can the battery produce a current of 0.85 microamp (10 −6 amp)?
The electrolysis of BiO+ produces pure bismuth. How long would it take to produce 10.0 g Bi by the electrolysis of a BiO+ solution using a current of 25.0 A?
Commercial electrolytic cells for producing aluminum operate at 5.0 V and 100,000 A.(a) How long does it take to produce exactly 1 metric ton (1000 kg) of aluminum?
A voltaic cell using Cu/Cu2+ and Sn/Sn2+ half-cells is set up at standard conditions, and each compartment has a volume of 345 mL. The cell delivers 0.17 A for 48.0 h.(b) What is the [Cu2+] remaining?
An aqueous solution of an unknown salt of ruthenium is electrolyzed by a current of 2.50 A passing for 50.0 min. If 2.618 g Ru is produced at the cathode, what is the charge on the ruthenium ions in solution?
If the Ecell of the following cell is 0.915 V, what is the pH in the anode compartment?Pt(s)│H2 (1.00 atm)│H+(aq)║Ag+ (0.100 M)│Ag(s)
What mass of each product is produced in each of the electrolytic cells below if a total charge of 3.33 × 105 C passes through each cell? Assume the voltage is sufficient to perform the reduction.(a) CaCl2(b) LiH(c) AlCl3(d) CrBr3
A current of 2.345 A passes through the cell shown in Figure 17.20 for 45 minutes. What is the volume of the hydrogen collected at room temperature if the pressure is exactly 1 atm? Assume the voltage is sufficient to perform the reduction.
An irregularly shaped metal part made from a particular alloy was galvanized with zinc using a Zn(NO3)2 solution. When a current of 2.599 A was used, it took exactly 1 hour to deposit a 0.01123-mm layer of zinc on the part. What was the total surface area of the part? The density of zinc is 7.140 g/cm3. Assume the efficiency is 100%.
Three electrolytic cells are connected in a series. The electrolytes in the cells are aqueous copper(II) sulfate, gold(III) sulfate, and silver nitrate. A current of 2.36 A is applied and after some time 1.74 g Cu is deposited. What mass of gold was deposited?
Calculate the pH of the cathode compartment for the following reaction given  εcell = 3.01 V when [Cr3+] = 0.15 M,[Al3+] = 0.30 M, and [Cr 2O72-] = 0.55 M.2Al (s) + Cr2O72-(aq) + 14H +(aq) → 2Al 3+(aq) + 2Cr 3+(aq) + 7H 2O(l)
The overall cell reaction occurring in an alkaline battery isZn(s) + MnO2(s) + H2O(l) ⟶ ZnO(s) + Mn(OH)2(s)(b) If 4.50 g of zinc is oxidized, how many grams of manganese dioxide and of water are consumed?(c) What is the total mass of reactants consumed in part (b)?
Gallium is produced by the electrolysis of a solution obtained by dissolving gallium oxide in concentrated NaOH(aq). Calculate the amount of Ga(s) that can be deposited from a  Ga(III) solution by a current of 0.730 A that flows for 40.0 min. 
A current of 3.07 A is passed through a Pb(NO3)2 solution. How long (in hours) would this current have to be applied to plate out 7.10 g of lead?
How many grams of Cu metal (63.55 g/mol) will be plated out of a Cu(NO3 )2 solution by passing a current of 3.00 amperes for 11 minutes? (1 Faraday = 96,485 Coulombs)1. 2.608 g2. 0.652 g 3. 1.304 g4. 0.0721 g
A current of 0.5 amp flows through an electrochemical cell that evolves Cl 2 gas by the oxidation of Cl1-. What number of moles of Cl 2 gas are generated in a period of 30 min?A) 900 moleB) 9.3 x10-3 moleC) 4.6 x10-3 moleD) 1.6 x 10-4 moleE) 7.8 x 10-5 mole 
Oxygen Supply in Submarines Nuclear submarines can stay under water nearly indefinitely because they can produce their own by the electrolysis of water. How many liters of O2 at 298 K and 1.00 bar are produced in 3.00 hr in an electrolytic cell operating at a current of 0.0200 A?
A current of 4.02 A is passed through a Ni(NO3)2 solution. How long (in hours) would this current have to be applied to plate out 6.20 g of nickel? 
For the following battery: Cd(s) | CdCl 2(aq) || Cl -(aq) | Cl2(l) | C(s)a) Write the reduction half reaction occuring at the C(s) electrode. (Include physical states of reactants and products.)b) Calculate the mass of Cl 2 consumed if the battery delivers a constant current of 713 A for 30.0 min.