Electron Transfer

Question 1

As the reduction potential for a molecule become more negative, it becomes a stronger __________.

Reducing agent or Oxidizing Agent

Answer 1

Reducing agent

(The oxidized form is thermodynamically more stable)

Question 2

Two of the same element in different oxidation states combine to the same oxidation.

Answer 2

Comproportionates

Pb(s) + Pb^IVO₂ + 2H₂SO₄ —–> Pb^IISO₄ + 2H₂O

Question 3

What oxidation state of Manganese is more stable under strongly basic conditions?

Answer 3

Oxidation state +3

Mn₂O₃

Question 4

If E_cell < 0, than the electron transfer reaction is __________.

Endergonic or Exergonic ​

Answer 4

Endergonic (non-spontaneous)

(Remember: ΔG^o = -nFE^o_cell)

Question 5

If E_cell > 0, than the electron transfer reaction is __________.

Endergonic or Exergonic ​

Answer 5

Exergonic (spontaneous)

(Remember: ΔG^o = -nFE^o_cell)

Question 6

Electron transfer that occurs with no direct bond between redox partners.

Answer 6

Outer Sphere Electron Transfer

Question 7

Electron transfer that occurs with the formation of bonds between redox partners and the bridging group often (though not always) transfers

Answer 7

Inner Sphere Electron Transfer

Question 8

Mixed valence compounds where the valence is completely delocalized.

Answer 8

Class III - Valence Delocalized

Question 9

Mixed valence compounds where there is some localization of distinct valences, but there is a low activation energy for their interconversion.

Answer 9

Class II - Intermediate

Question 10

Compounds where the valences are trapped—localized on a single site.

Answer 10

Class 1-Valence Localized​

Question 11

What type of equilibrium exist between species across diagonal boundary lines in a Pourbaix diagram?

Answer 11

Proton Dependent Redox Reactions

Question 12

What type of equilibrium exist between species across horizontal boundary lines in a Pourbaix diagram?

Answer 12

Proton Independent Redox Reactions

Question 13

What type of equilibrium exist between species across vertical boundary lines in a Pourbaix diagram?

Answer 13

Acid-Base Equilibriums

Question 14

According to Marcus Theory, an increase in driving force leads to an increase in electron transfer rate in this region?

Answer 14

The Normal Region

(Classical Region)

Question 15

The biomolecular rate constants for outer-sphere self exhange mechanism tend to be ________ if they involve electron transfer to and from low lying antibonding orbitals.

Fast or Slow

Answer 15

Slow

Large changes in bond lengths are expected and therefore inter-sphere reorganization energy will be large

Question 16

The parabolic potentials curve represent the_________.

Answer 16

Potential energy for vibrational states as a funtions of nuclear coordinates.

Question 17

The parameter β in Dutton’s Ruler represents the _______ in which the electron propagates.

Answer 17

Medium

Question 18

The proton and electron always propagate in the same directions in proton coupled electron transfer reactions.

True or False

Answer 18

False

Question 19

A chemical reaction that involves the transfer of both an electron and a proton at roughly the same time.

Answer 19

Proton Coupled Electron Transfer (PCET)

Note: This process lowers the free energy of successive electron transfers by creating a nearly charge neutral process.

Question 20

What is the voltage shift between each successive reduction with proton coupled electron transfer?

Answer 20

~400-600 mV shift per charge unit

Question 21

According to Marcus Theory, an increase in driving force leads to a decrease in electron transfer rates in this region?

Answer 21

The Inverted Region

(Note: Driving force is equal to the reorganization energy (λ) in this region)

Question 22

According to Marcus Theory, this region is where driving force is equal to the reorganization energy in this region?

Answer 22

The Activtionless Region

Question 23

The reorganization energy that can be assoicated with the rearrangement of the solvent surrounding the electron transfer centers.

Answer 23

Outer-Sphere Reorganization Energy

Question 24

The reorganization energy that can be assoicated with the instrictic geometry change that occurs on a redox center.

Answer 24

Inner Sphere Reorganization Energy

Question 25

**As the distance between an electron donor and an acceptor increases, the rate of electron transfer\_\_\_\_\_\_.** **Increases or Decreases**

Answer 25

**Decreases**

Question 26

**For a one electron transfer reation that is *reversible*, what is the seperation between the oxidation peak potenital (E_pa) and reduction peak potenital (E_pc)?**

Answer 26

**59mV**

Question 27

**In the Pourbaix diagram for Mn, which boundary line represents the following equilibrium:** **Mn ⇌** **Mn(II) + 2e^-**

Answer 27

## Footnote **This boundary line is horizontal and therefore electrons are transfered in the equilibrium with no proton depencence.**

Question 28

**Mn⁺² under acidic conditions is stable to \_\_\_\_\_\_\_\_\_.** ***Conproportionation or Disproportionation***

Answer 28

## Footnote ***Conproportionation*** *If the species of interest lies below the line connecting it's two adjacent species on a Frost Diagram, the two adjacent species are unstable with respect to conproportionation.*

Question 29

**Mn⁺³ under acidic conditions is unstable to \_\_\_\_\_\_\_\_\_.** ***Conproportionation or Disproportionation***

Answer 29

## Footnote ***Disproportionation*** *If the species of interest lies above the line connecting the two adjacent species on a Frost Diagram, that species is unstable with respect to disproportionation*

Question 30

**One compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation states**

Answer 30

## Footnote **Disproportionate** **Hg₂Cl₂ → Hg + HgCl₂**

Question 31

***E=E^o-(RT/nF)\*ln([Red]/[Ox])***

Answer 31

***Nernst Equation*** ## Footnote ***E^o-*** the standard cell potential ***E***-cell potential ***F***- Faraday constant ***n***- number of electrons

Question 32

***Idenifity the following feature of a cyclic voltammogram​***

Answer 32

***E_pc*** *The anodic peak potential*

Question 33

***Idenifity the following feature of a cyclic voltammogram​***

Answer 33

***E_pc*** *The Cathodic peak potential*

Question 34

***Idenifity the following feature of a cyclic voltammogram​***

Answer 34

***E_1/2 ( in V)*** Estimate of the formal redox potential under a specfic set of conditions

Question 35

## Footnote ***Idenifity the following feature of a cyclic voltammogram​***

Answer 35

***Reduction Event***

Question 36

## Footnote ***Idenifity the following feature of a cyclic voltammogram​***

Answer 36

***Oxidation Event***

Question 37

## Footnote **As the reduction potential for a molecule become more positive, it becomes a stronger \_\_\_\_\_\_\_\_\_\_.** ***Reducing agent or Oxidizing Agent***

Answer 37

***Oxidizing agent*** ***(The reduced form is ​thermodynamically more stable)***