Electrode Potentials And Fuel Cells

Question 1

Definition of reduction

Answer 1

A gain of electrons, or a decrease in oxidation number

Question 2

Oxidation number rules:

Uncombined element

Answer 2

0

Question 3

Oxidation number rules:

Combined oxygen

Answer 3

-2

Question 4

Oxidation number rule:

Combined hydrogen

Answer 4

+1

Question 5

Oxidation number rules:

Simple ion

Answer 5

Ionic charge of ion

Question 6

Oxidation number rule:

Combined fluorine

Answer 6

-1

Question 7

Construct redox equation using:
Fe-> Fe3+ + 3e-
Cu2+ + 2e- -> Cu

Answer 7

3Cu2+ + 2Fe -> 3Cu + 2Fe3+

Question 8

Define standard electrode potential

Answer 8

The emf of a half cell compared with a standard hydrogen cell, measured at 298K with solution concentrations of 1moldm^-3 and a gas pressure of 100kPa

Question 9

Feasability of reactions using standard cell potentials

Answer 9

The more negative half cell equation will be flipped to put reactants and products on the right sides

Question 10

Limitations of technique to find feasability

Answer 10

Non-standard conditions- altering concentrations due to shifts in equilibrium so more/less electrons produced, so electrode potential changes.
-may not happen
•can predict position but not reaction rate which could be slow
•actual conditions used may be different
•standard electrode potentials apply to aqueous equilibria, most are not like this in reality

Question 11

Definition of oxidation

Answer 11

Loss of electrons or an increase in oxidation number