Electrode and Cell Potentials

Electrode and Cell Potentials

by Luis Bello

Previous Class​

Galvanic Cells​

Multiple Choice

In a Galvanic Cell, the anode is...

• positive

• negative

Multiple Choice

In a Galvanic Cell, the cathode is...

• positive

• negative

Multiple Choice

Oxidation occurs at the...

• anode

• cathode

Multiple Choice

Reduction occurs at the...

• anode

• cathode

Multiple Choice

In the above Galvanic Cell, which half cell is undergoing reduction?

• Cu | Cu²⁺

• Zn | Zn²⁺

Multiple Choice

A certain galvanic cell has for its spontaneous cell reaction: Zn + HgO → ZnO + Hg

Which is the half-reaction occurring at the cathode?

• HgO + 2 e- → Hg + O^2-

• Hg → Hg²⁺ + 2 e-

• Zn → Zn²⁺ + 2 e-

• ZnO + 2 e- → Zn

Multiple Choice

Consider the galvanic cell given.
Which of the following deductions about this cell is correct?

• Oxidation is occurring in half-cell 2
• The positive electrode is in half-cell 2
• Oxidation is occurring in half-cell 1
• The negative electrode is in half-cell 1

Multiple Choice

Consider the galvanic cell represented, operating at 25^oC , 101.3 kPa and using 1 M solutions. 
The product(s) of the half-reaction occurring in half-cell 1 is (are)

• Ni (s)
• Ni²⁺ (aq)
• H₂O₂ (aq)/H⁺ (aq)
• H₂O (l)

Multiple Choice

A galvanic cell is established to power a torch, as shown.
For this cell, the overall equation will be

• 2Al(s)+3H_2(g)→2Al³⁺(aq)+6H⁺(aq)
• 3Cl^-(aq)+Al(s)→AlCl₃(aq)
• 2Al³⁺(aq)+3H_2(g)→2Al(s)+6H⁺(aq)
• 2Al(s)+6H⁺(aq)→2Al³⁺(aq)+3H₂(g)

​Learning Objetives

• Describe and relate the definitions of electrode and cell potentials

• Interpret electrode potentials in terms of relative oxidant and reductant strengths

• Calculate cell potentials and predict redox spontaneity using standard electrode potentials

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​The electrode potential

​In electrochemistry, the electrode potential is the electromotive force of a galvanic cell built from a standard reference electrode and another electrode to be characterized.

​

By convention, the reference electrode is the standard hydrogen electrode (SHE). It is defined to have a potential of zero volts.

​​The SHE electrode

​The SHE electrode can be connected to any other electrode by a salt bridge to form a cell.

​

If the second electrode is also at standard conditions, then the measured cell potential is called the standard electrode potential for the electrode.

The standard electrode potential for the SHE is zero, by definition.

​Standard electrode potentials

​Standard electrode potentials reflect the relative oxidizing strength of the half-reaction reactant, with stronger oxidants exhibiting larger (more positive) E°_X values. Tabulations of standard electrode potentials may be used to compute standard cell potentials, E°_cell, for many redox reactions.

Multiple Choice

• -0.41V

• -0.27 V

• +0.27 V

• +0.41 V

Multiple Choice

The relevant standard electrode potentials for this cell are shown below.

Cr3+(aq) + 3e- ⇌ Cr(s) E= − 0.74 V

Ag+(aq) + e− ⇌ Ag(s) E = + 0.80 V

Calculate the emf of the cell shown in the diagram.

• +1.54 V

• -1.54 V

• + 0.06 V

• - 0.06 V

Multiple Choice

Which species will oxidise Fe²⁺(aq) to Fe³⁺(aq)?

• Br_{2 (aq)}

• Cl^-_(aq)

• I_{2 (aq)}

• Mn²⁺_(aq)

Multiple Choice

Calculate the emf for the reaction between MnO₄^– ions and Br^– ions in acidic solution.

• -0.42 V

• +0.42 V

• +2.60 V

• -2.60 V

Multiple Choice

The standard electrode potentials of two half reactions are shown.

Which of the following processes is thermodynamically favourable? The reaction of

• Co²⁺ with Cl₂ to form Cl⁻

• Co²⁺ with Cl⁻ to form Cl₂

• Co³⁺ with Cl₂ to form Cl⁻

• Co³⁺ with Cl⁻ to form Cl₂

Multiple Choice

Calculate the cell potential of a galvanic cell that uses the two half equation below

Sn²⁺ + 2e^- --> Sn⁴⁺ E⁰ = -0.14 V

Mg²⁺ + 2e^- --> Mg E⁰ = -2.37 V

• -2.23 V

• -2.51 V

• + 2.23 V

Multiple Choice

Using the following standard reduction potentials

Fe³⁺(aq) + e --> Fe²⁺(aq) + e E⁰ = +0.77V

Ni²⁺ + 2e --> Ni E⁰ = -0.26V

Ni + 2 Fe³⁺ --> Ni²⁺ + 2 Fe²⁺

Calculate the standard cell potential for the above galvanic cell

• -1.8V

• +1.8V

• +0.51 V