A-Level Chemistry: Electrochemistry Objectives

 6.1 Redox processes: electron transfer and changes in oxidation number (oxidation state)

a) calculate oxidation numbers of elements in compounds and ions

b) describe and explain redox processes in terms of electron transfer and changes in oxidation number

c) use changes in oxidation numbers to help balance chemical equations

6.2 Electrolysis

a) state and apply the relationship F = Le between the Faraday constant, the Avogadro constant and the charge on the electron

b) predict the identity of the substance liberated during electrolysis from the state of electrolyte (molten or aqueous), position in the redox series (electrode potential) and concentration

c) calculate:

(i) the quantity of charge passed during electrolysis

(ii) the mass and/or volume of substance liberated during electrolysis, including those in the electrolysis of H2SO4(aq) and of Na2SO4(aq)

d) describe the determination of a value of the Avogadro constant by an electrolytic method

 6.3 Standard electrode potentials E⦵ : standard cell potentials E⦵ cell  and the Nernst equation

a) define the terms:

(i) standard electrode (redox) potential

(ii) standard cell potential

b) describe the standard hydrogen electrode

c) describe methods used to measure the standard electrode potentials of:

(i) metals or non-metals in contact with their ions in aqueous solution

(ii) ions of the same element in different oxidation states

d) calculate a standard cell potential by combining two standard electrode potentials

e) use standard cell potentials to:

(i) explain/deduce the direction of electron flow in a simple cell

(ii) predict the feasibility of a reaction

f) deduce from E ⦵  values the relative reactivity of elements of Group 17 (the halogens) as  oxidising agents

g) construct redox equations using the relevant half-equations

h) predict qualitatively how the value of an electrode potential varies with the concentrations of the aqueous ions

i) use the Nernst equation, e.g. E  = E⦵  + (0.059/z) log [oxidised species]/[reduced species]

to predict quantitatively how the value of an electrode potential varies with the concentrations of the aqueous ions; examples

include Cu(s) + 2e– ⇌  Cu2+ (aq), Fe3+ (aq) + e– ⇌  Fe2+ (aq),

Cl2 (g) + 2e– ⇌  2Cl– (aq)

6.4 B atteries and fuel cells

a) state the possible advantages of developing other types of cell, e.g. the H2 /O2  fuel cell and the nickel-metal hydride and lithium-ion rechargeable batteries

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