University of Kentucky Clicker Questions Chapter 18 Electrochemistry Allison Soult University of Kentucky

Fe2+ (aq) + MnO4– (aq) → Fe3+ (aq) + Mn2+ (aq) What is the coefficient of Fe2+ when the following redox equation is balanced? Fe2+ (aq) + MnO4– (aq) → Fe3+ (aq) + Mn2+ (aq) 1 2 3 4 5 Answer: e

Fe2+ (aq) + MnO4– (aq) → Fe3+ (aq) + Mn2+ (aq) What is the coefficient of Fe2+ when the following redox equation is balanced? Fe2+ (aq) + MnO4– (aq) → Fe3+ (aq) + Mn2+ (aq) 1 2 3 4 5 Answer: e

The following reaction occurs in a lead storage battery The following reaction occurs in a lead storage battery. How many moles of electrons are transferred in the following balanced redox equation per reaction cycle? Pb (s) + PbO2 (aq) + 2 HSO4– (aq) + 2 H+ (aq) → 2 PbSO4 (s) + 2 H2O (l) 2.34 1.35 1.30 2.41 Answer: b

The following reaction occurs in a lead storage battery The following reaction occurs in a lead storage battery. How many moles of electrons are transferred in the following balanced redox equation per reaction cycle? Pb (s) + PbO2 (aq) + 2 HSO4– (aq) + 2 H+ (aq) → 2 PbSO4 (s) + 2 H2O (l) 2.34 1.35 1.30 2.41 Answer: b

How many water molecules will there be when MnO4– + CN–  MnO2 + CNO– is balanced in base? 4 on the reactant side 4 on the product side 2 on the reactant side 2 on the product side Answer: c

How many water molecules will there be when MnO4– + CN–  MnO2 + CNO– is balanced in base? 4 on the reactant side 4 on the product side 2 on the reactant side 2 on the product side Answer: c

All of the above would function as cathodes. Which transformation could take place at the anode of an electrochemical cell? NO → NO3– VO2+ → VO2+ O2 → H2O2 All of the above would function as cathodes. All of the above would function as anodes. Answer: a

All of the above would function as cathodes. Which transformation could take place at the anode of an electrochemical cell? NO → NO3– VO2+ → VO2+ O2 → H2O2 All of the above would function as cathodes. All of the above would function as anodes. Answer: a

The purpose of the salt bridge in an electrochemical cell is to maintain electrical neutrality in the half-cells via migration of ions. to provide a source of ions to react at the anode and cathode. to provide oxygen to facilitate oxidation at the anode. to provide a means for electrons to travel from the anode to the cathode. to provide a means for electrons to travel from the cathode to the anode. Answer: a

The purpose of the salt bridge in an electrochemical cell is to maintain electrical neutrality in the half-cells via migration of ions. to provide a source of ions to react at the anode and cathode. to provide oxygen to facilitate oxidation at the anode. to provide a means for electrons to travel from the anode to the cathode. to provide a means for electrons to travel from the cathode to the anode. Answer: a

Ni (s) | Ni2+ (aq) || Ag+ (aq) | Ag (s) What is the reducing agent in the following electrochemical cell? Ni (s) | Ni2+ (aq) || Ag+ (aq) | Ag (s) Ni Ni2+ Ag Ag+ There is no reducing agent in an electrochemical cell. Answer: a

Ni (s) | Ni2+ (aq) || Ag+ (aq) | Ag (s) What is the reducing agent in the following electrochemical cell? Ni (s) | Ni2+ (aq) || Ag+ (aq) | Ag (s) Ni Ni2+ Ag Ag+ There is no reducing agent in an electrochemical cell. Answer: a

Ni2+ (aq) + 2 e– → Ni (s) –0.23 V Zn2+ (aq) + 2 e– → Zn (s) –0.76 V Which of the following is the best reducing agent? Ni2+ Ni Zn Ag Ni2+ (aq) + 2 e– → Ni (s) –0.23 V Zn2+ (aq) + 2 e– → Zn (s) –0.76 V Ag+ (aq) + e– → Ag (s) 0.80 V Answer: c

Ni2+ (aq) + 2 e– → Ni (s) –0.23 V Zn2+ (aq) + 2 e– → Zn (s) –0.76 V Which of the following is the best reducing agent? Ni2+ Ni Zn Ag Ni2+ (aq) + 2 e– → Ni (s) –0.23 V Zn2+ (aq) + 2 e– → Zn (s) –0.76 V Ag+ (aq) + e– → Ag (s) 0.80 V Answer: c

Mg (s) + Cu2+ (aq) → Cu (s) + Mg2+ (aq) Calculate the cell potential for the following reaction under standard conditions: Mg (s) + Cu2+ (aq) → Cu (s) + Mg2+ (aq) +2.04 –2.04 +2.71 –1.36 +1.36 Cu2+ (aq) + 2 e– → Cu (s) 0.34 V Mg2+ (aq) + 2 e– → Mg (s) –2.37 V Answer: c

Mg (s) + Cu2+ (aq) → Cu (s) + Mg2+ (aq) Calculate the cell potential for the following reaction under standard conditions: Mg (s) + Cu2+ (aq) → Cu (s) + Mg2+ (aq) +2.04 –2.04 +2.71 –1.36 +1.36 Cu2+ (aq) + 2 e– → Cu (s) 0.34 V Mg2+ (aq) + 2 e– → Mg (s) –2.37 V Answer: c

Which of the following metals will dissolve in nitric acid but not in hydrochloric acid? Au Ag Fe Pb Ni Answer: b

Which of the following metals will dissolve in nitric acid but not in hydrochloric acid? Au Ag Fe Pb Ni Answer: b

2 Al (s) + 3 I2 (s) → 2 Al3+ (aq) + 6 I– (aq) Consider a cell that employs the following overall reaction: What is ΔG° for the cell? 2 Al (s) + 3 I2 (s) → 2 Al3+ (aq) + 6 I– (aq) I2 (s) + 2 e– → 2 I– (aq) 0.54 Al3+ (aq) + 3 e– → Al (s) –1.66 636 kJ/mol –648 kJ/mol –216 kJ/mol –636 kJ/mol –1270 kJ/mol Answer: e

2 Al (s) + 3 I2 (s) → 2 Al3+ (aq) + 6 I– (aq) Consider a cell that employs the following overall reaction: What is ΔG° for the cell? 2 Al (s) + 3 I2 (s) → 2 Al3+ (aq) + 6 I– (aq) I2 (s) + 2 e– → 2 I– (aq) 0.54 Al3+ (aq) + 3 e– → Al (s) –1.66 636 kJ/mol –648 kJ/mol –216 kJ/mol –636 kJ/mol –1270 kJ/mol Answer: e

What is the value of the equilibrium constant when the cell potential is found to be −0.29 V for a transfer of 2 moles of electrons? 1.6 × 10–10 0.56 0.72 0.87 6.4 × 10–2 Answer: a

What is the value of the equilibrium constant when the cell potential is found to be −0.29 V for a transfer of 2 moles of electrons? 1.6 × 10–10 0.56 0.72 0.87 6.4 × 10–2 Answer: a

Calculate the cell potential (Ecell) of an electrochemical cell at 298 K with Mg/Mg2+ and Fe/Fe2+ electrodes. [Mg2+] = 0.200 M and [Fe2+] = 0.050 M. Fe2+ (aq) + 2 e– → Fe (s) –0.45 Mg2+ (aq) + 2 e– → Mg (s) –2.37 1.90 1.92 1.94 2.82 2.80 Answer: a

Calculate the cell potential (Ecell) of an electrochemical cell at 298 K with Mg/Mg2+ and Fe/Fe2+ electrodes. [Mg2+] = 0.200 M and [Fe2+] = 0.050 M. Fe2+ (aq) + 2 e– → Fe (s) –0.45 Mg2+ (aq) + 2 e– → Mg (s) –2.37 1.90 1.92 1.94 2.82 2.80 Answer: a

A concentration cell is assembled with a copper anode and cathode A concentration cell is assembled with a copper anode and cathode. One cell has [Cu2+] = 0.25 M and the other has [Cu2+] = 2.5 M. What is the cell potential? 0 V −0.030 V 0.030 V − 0.0592 V 0.0592 V Answer: c

A concentration cell is assembled with a copper anode and cathode A concentration cell is assembled with a copper anode and cathode. One cell has [Cu2+] = 0.25 M and the other has [Cu2+] = 2.5 M. What is the cell potential? 0 V −0.030 V 0.030 V − 0.0592 V 0.0592 V Answer: c

What mass of nickel can be plated from a solution containing Ni2+ with a current of 3.6 A for 14 minutes? 0.92 g 1.8 g 3.7 g 1.0 g 0.071 g Answer: a

What mass of nickel can be plated from a solution containing Ni2+ with a current of 3.6 A for 14 minutes? 0.92 g 1.8 g 3.7 g 1.0 g 0.071 g Answer: a

Au3+ (aq) + 3 e– → Au (s) 1.50 V Cu2+ (aq) + 2 e– → Cu (s) 0.34 V Which of the following is the best sacrificial electrode for iron? Au3+ (aq) + 3 e– → Au (s) 1.50 V Au Cu Ni Pb Mg Cu2+ (aq) + 2 e– → Cu (s) 0.34 V Fe3+ (aq) + 3 e– → Fe (s) –0.036 V Pb2+ (aq) + 2 e– → Pb (s) –0.13 V Answer: e Ni2+ (aq) + 2 e– → Ni (s) –0.23 V Mg2+ (aq) + 2 e– → Mg (s) –2.37 V

Au3+ (aq) + 3 e– → Au (s) 1.50 V Cu2+ (aq) + 2 e– → Cu (s) 0.34 V Which of the following is the best sacrificial electrode for iron? Au3+ (aq) + 3 e– → Au (s) 1.50 V Au Cu Ni Pb Mg Cu2+ (aq) + 2 e– → Cu (s) 0.34 V Fe3+ (aq) + 3 e– → Fe (s) –0.036 V Pb2+ (aq) + 2 e– → Pb (s) –0.13 V Answer: e Ni2+ (aq) + 2 e– → Ni (s) –0.23 V Mg2+ (aq) + 2 e– → Mg (s) –2.37 V