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Date November 2017 Marks available 1 Reference code 17N.2.hl.TZ0.7
Level HL Paper 2 Time zone TZ0
Command term Identify Question number 7 Adapted from N/A

Question

Consider the following half-cell reactions and their standard electrode potentials.

Deduce a balanced equation for the overall reaction when the standard nickel and iodine half-cells are connected.

[1]
a.

Predict, giving a reason, the direction of movement of electrons when the standard nickel and manganese half-cells are connected.

[2]
b.

Calculate the cell potential, in V, when the standard iodine and manganese half-cells are connected.

[1]
c.

Identify the best reducing agent in the table above.

[1]
d.

State and explain the products of electrolysis of a concentrated aqueous solution of sodium chloride using inert electrodes. Your answer should include half-equations for the reaction at each electrode.

[4]
e.

Markscheme

Ni (s) + I2 (aq) → 2I(aq) + Ni2+ (aq)

a.

electron movement «in the wire» from Mn(s) to Ni(s)

Eθ «for reduction» of Ni2+ is greater/less negative than Eθ «for reduction» of Mn2+

OR

Ni2+ is stronger oxidizing agent than Mn2+

OR

Mn is stronger reducing agent than Ni

b.

«0.54 V – (–1.18 V) = +»1.72 «V»

Do not accept –1.72 V.

c.

Mn «(s)»

d.

Positive electrode (anode):
2Cl (aq) → Cl2 (g) + 2e

Cl oxidized because higher concentration

OR

electrode potential/E depends on concentration

OR

electrode potential values «of H2O and Cl» are close

Negative electrode (cathode):
2H2O (l) + 2e → H2 (g) + 2OH (aq)

OR

2H(aq) + 2e → H2 (g)

H2O/H+ reduced because Na+ is a weaker oxidizing agent

OR

Na+ not reduced to Na in water

OR

H+ easier to reduce than Na+
OR

H lower in activity series «than Na»

Accept .

e.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.
[N/A]
d.
[N/A]
e.

Syllabus sections

Core » Topic 9: Redox processes » 9.1 Oxidation and reduction
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