Name Electrochemical Cells Practice Exam Date:

Transcription

1 Name Electrochemical Cells Practice Exam Date: 1. Which energy change occurs in an operating voltaic cell? 1) chemical to electrical 2) electrical to chemical 3) chemical to nuclear 4) nuclear to chemical 2. What is the voltage for a chemical cell that has reached equilibrium? 1) 1.00 V 2) greater than 1.00 V 3. Which half-reaction can occur at the anode in a voltaic cell? 1) Ni e - Ni 3) Zn Zn e - 2) Sn + 2e - Sn 2+ 4) Fe 3+ Fe 2+ + e - 4. Which statement is true for any electrochemical cell? 1) Oxidation occurs at the anode, only. 2) Reduction occurs at the anode, only. 3) Oxidation occurs at both the anode and the cathode. 4) Reduction occurs at both the anode and the cathode. 3) greater than 0.00 V and less than 1.00 V 4) 0.00 V 5. Base your answer to the following question on the diagram of the chemical cell at 298 K and on the equation below. In the given reaction, the Ag + ions 1) gain electrons 2) lose electrons 3) gain protons 4) lose protons 6. The electricity produced by a battery results from 1) an oxidation reaction, only 2) a reduction reaction, only 3) both an oxidation reaction and a reduction reaction 4) neither an oxidation reaction nor a reduction reaction 7. When a voltaic cell operates, ions move through the 1) anode 2) cathode 3) salt bridge 4) external circuit

2 8. Which component of an electrochemical cell is correctly paired with its function? 1) external conductor allows the solutions to mix 2) external conductor permits the migration of ions 3) salt bridge allows the solutions to mix 4) salt bridge permits the migration of ions 9. The diagram below represents an electrochemical cell. What occurs when the switch is closed? 1) Zn is reduced. 2) Cu is oxidized. 10. The diagram below represents a chemical cell at 298 K. 3) Electrons flow from Cu to Zn. 4) Electrons flow from Zn to Cu. When the switch is closed, electrons flow from 1) Al(s) to Ni(s) 2) Ni(s) to Al(s) 3) Al 3+ (aq) to Ni 2+ (aq) 4) Ni 2+ (aq) to Al 3+ (aq)

3 11. Base your answer to the following question on the diagram of the chemical cell shown below. The reaction occurs at 1 atmosphere and 298 K. When the switch is closed, what occurs? 1) Pb is oxidized and electrons flow to the Zn electrode. 2) Pb is reduced and electrons flow to the Zn electrode. 3) Zn is oxidized and electrons flow to the Pb electrode. 4) Zn is reduced and electrons flow to the Pb electrode. 12. Which energy conversion occurs in an operating electrolytic cell? 1) chemical energy to electrical energy 2) electrical energy to chemical energy 13. Which reaction occurs at the cathode in an electrochemical cell? 3) nuclear energy to thermal energy 4) thermal energy to nuclear energy 1) combustion 2) neutralization 3) oxidation 4) reduction 14. The diagram below shows a key being plated with copper in an electrolytic cell Given the reduction reaction for this cell: Cu 2+ (aq) + 2e - Cu(s) This reduction occurs at 1) A, which is the anode 2) A, which is the cathode 3) B, which is the anode 4) B, which is the cathode

4 15. Which process requires an external power source? 1) neutralization 2) synthesis 3) fermentation 4) electrolysis 16. Which statement best describes the key? 1) It acts as the cathode and is negative. 2) It acts as the cathode and is positive. 17. Given the redox reaction: 3) It acts as the anode and is negative. 4) It acts as the anode and is positive. 2 Cr(s) + 3 Cu 2+ (aq) 2 Cr 3+ (aq) + 3 Cu(s) Which reaction occurs at the cathode in an electrochemical cell? 1) reduction of Cu 2+ (aq) 2) reduction of Cu(s) 3) oxidation of Cr 3+ (aq) 4) oxidation of Cr(s) 18. Base your answer to the following question on the diagram below which represents the electroplating of a metal fork with Ag(s). Which equation represents the half-reaction that takes place at the fork? 1) Ag + + NO3 AgNO3 3) Ag + + e Ag(s) 2) AgNO3 Ag + + NO3 4) Ag(s) Ag + + e 19. The reaction 2 H2O ( ) 2 H2(g) + O2(g) is forced to occur by use of an externally applied electric current. This procedure is called 1) neutralization 2) esterification 3) electrolysis 4) hydrolysis

5 20. Which equation represents the half-cell reaction that occurs at the negative electrode during the electrolysis of fused calcium chloride? 1) Ca 2+ Ca(s) + 2e 2) Ca e Ca(s) Base your answers to questions 21 and 22 on the information below. 3) 2 Cl + 2e Cl2(g) 4) 2 Cl Cl2(g) + 2e A student constructs an electrochemical cell during a laboratory investigation. When the switch is closed, electrons flow through the external circuit. The diagram and equation below represent this cell and the reaction that occurs. 21. State, in terms of energy, why this cell is a voltaic cell. 22. State the direction of electron flow through the wire when the switch is closed.

6 Base your answers to questions 23 through 25 on the information below. The diagram below represents an operating electrolytic cell used to plate silver onto a nickel key. As the cell operates, oxidation occurs at the silver electrode and the mass of the silver electrode decreases. 23. Explain, in terms of Ag atoms and Ag + (aq) ions, why the mass of the silver electrode decreases as the cell operates. 24. State the purpose of the power source in the cell. 25. Identify the cathode in the cell.

7 Answer Key Electrochemical Cells Practice Exam —A spontaneous reaction converts chemical energy to electrical energy. —A battery is not required to provide energy for the cell to operate. 22. Electrons flow from the Al electrode to the Ni electrode. Electrons move left to right through the wire. 23. —Silver atoms lose electrons and become silver ions in the solution. — Some of the Ag atoms become Ag + ions. —Silver atoms are oxidized to silver ions. 24. —The cell requires electrical energy for the non-spontaneous reaction to occur. —The power source causes some Ag(s) atoms to oxidize. 25. Ni(s) key / nickel