ELECTROCHEMICAL CELLS ASSIGNMENT

Which statement is true of a galvanic cell?

Electrons travel from cathode to anode, reduction occurs at the anode, the cathode is the negative electrode, and the reaction is nonspontaneous

Electrons travel from anode to cathode, reduction occurs at the cathode, the anode is the negative electrode, and the reaction is spontaneous

Electrons travel from anode to cathode, reduction occurs at the cathode, the anode is the negative electrode, and the reaction is nonspontaneous

Electrons travel from anode to cathode, oxidation occurs at the cathode, the cathode is the negative electrode, and the reaction is spontaneous

Electrons travel from cathode to anode, oxidation occurs at the anode, the anode is the negative electrode, and the reaction is spontaneous

Correct answer:Electrons travel from anode to cathode, reduction occurs at the cathode, the anode is the negative electrode, and the reaction is spontaneous

Explanation:Galvanic cells always involve spontanous oxidation-reduction reactions. In any electrochemical cell, the electrons always move from anode to cathode. Also, the anode is always the site of oxidation, and the cathode is always the site of reduction. Since the reaction is spontaneous (net release of free energy) it drives the movement of electrons from the anode to the cathode. Remember, oxidation is loss of electrons and reduction is gain of electrons. Since oxidation always occurs at the anode, we are left with an excess of electrons, making it the negative electrode. It should makes sense that the extra electrons from the anode spontaneously travel to the cathode (positive electrode).

To help remember oxidation-reduction processes, consider the mnemonics “OIL RIG” and “An Ox, Red Cat.” OIL RIG stands for “oxidation is loss, reduction is gain” in reference to electrons. An Ox, Red Cat tells us that the anode is the site of oxidation, while the cathode is the site of reduction.

Which of the following differences between galvanic cells and electrolytic cells is false?

Possible Answers:

Electrolytic cells have a positive Gibb’s free energy

Electrolytic cells are non-spontaneous

Electrolytic cells have oxidation take place at the cathode

Electrolytic cells have negative voltages

Correct answer:Electrolytic cells have oxidation take place at the cathode

Explanation:Electrolytic cells use non-spontaneous reactions that require an external power source in order to proceed. The values between galvanic and electrolytic cells are opposite of one another. Galvanic cells have positive voltage potentials, while electrolytic voltage potentials are negative. Both types of cell, however, have oxidation occur at the cathode and reduction occur at the anode.

Li+(aq)+eLi(s)                  εo=3.04

Mg2+(aq)+2eMg(s)         εo=2.38

For the following reaction to occur does the does the electrochemical cell voltaic or galvanic?

2Li(s)+Mg2+(aq)2Li+(aq)+Mg(s)

Possible Answers:

Electrolytic

Both

Neither

Galvanic

Correct answer:Galvanic

Explanation:First we must rearrange the reduction potentials so that when added together, they match the reaction that takes place in the electrochemical cell.

Mg2+(aq)+2eMg(s)

In the overall reaction, Li(s) is in the reactant side, so the Li(s) equation must be inverted.

Li(s)Li+(aq)+e

Use the equation: εorxn=εoproductsεoreactants to find the εorxn.

Mg(s) is product, while Li(s) is the reactant.

εorxn=2.38(3.04)=0.66

The cell must be galvanic because the εorxn value is positive. This means, this the reaction is a spontaneous reaction occurs without an outside energy source.

Mugisa Geofrey and SOLOMON TATWEBWA

Mugisa Geofrey Zziwa is a learning facilitator with Ultimate MultiMedia Consult. With knowledge of the following topics:  Digital Pedagogy training or digital teaching skills, how to integrate ICT in teaching.  Journalism and the Internet/Computers (How internet helps journalism)  Basic web design & CMS and Multimedia Content publishing  Digital security and safety basics for journalists  Best practices for ensuring safety online  Data Mashups  Collaborative digital content development tools  Live streaming and Live reporting  Immersive Storytelling tools and practices  Among others I have conducted a number of trainings which include: • Multimedia Journalism and Digital Safety training for university Students held in Makerere University, Kampala International University and Cavendish University and sponsored by the American Embassy Uganda. • Digital Pedagogy training for Science Technology Engineering and Mathematics (STEM) Teachers held in Iganga Girls SSS in Iganga District for Eastern region Uganda, St. Maria Gorretti in MPigi District for Central region Uganda, and Teso College ALOET for the Karamoja region Uganda. Sponsored by Forum for African Women Educationalists Uganda (FAWEU) Training Teachers on integration of ICT in teaching and delivering lessons to students. • Digital Pedagogy at American Center for Teachers by Teachers In Need (TIN) Uganda. • Facilitator on Digital Pedagogy with ICT Teachers Association Uganda (ITAU) at American Center, Kyebambe Girls SSS in FortPortal for western region Uganda, Dr. Obote College Boro Boro Lira for Nothern Region Uganda.

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