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Date	May 2017	Marks available	1	Reference code	17M.2.hl.TZ1.3
Level	HL	Paper	2	Time zone	TZ1
Command term	Formulate	Question number	3	Adapted from	N/A

Question

Vanadium has a number of different oxidation states.

Electrode potentials for the reactions of vanadium and other species are shown below.

Determine the oxidation state of vanadium in each of the following species.

M17/4/CHEMI/HP2/ENG/TZ1/03.a

[2]

Identify, from the table, a non-vanadium species that can reduce VO²⁺(aq) to V³⁺(aq) but no further.

[1]

b.i.

Identify, from the table, a non-vanadium species that could convert ${\text{VO}}_2^ + {\text{(aq)}}$ to V²⁺(aq).

[1]

b.ii.

Formulate an equation for the reaction between VO²⁺(aq) and V²⁺(aq) in acidic solution to form V³⁺(aq).

[1]

c.i.

Comment on the spontaneity of this reaction by calculating a value for $\Delta {G^\theta }$ using the data given in (b) and in section 1 of the data booklet.

[3]

c.ii.

Markscheme

${V_2}{O_5}:{\text{ }} + 5$
$V{O^{2 + }}:{\text{ }} + 4$

Do not penalize incorrect notation twice.

[2 marks]

H₂SO₃(aq)
OR
Pb(s)

[1 mark]

b.i.

Zn(s)

[1 mark]

b.ii.

${\text{V}}{{\text{O}}^{2 + }}({\text{aq)}} + {{\text{V}}^{2 + }}({\text{aq)}} + {\text{2}}{{\text{H}}^ + }({\text{aq)}} \to {\text{2}}{{\text{V}}^{3 + }}({\text{aq)}} + {{\text{H}}_{\text{2}}}{\text{O(l)}}$

Accept equilibrium sign.

[1 mark]

c.i.

${E^\theta }\ll = + 0.34{\text{ V}} - ( - 0.26{\text{ V}})\gg = + 0.60{\text{ }}\ll {\text{V}}\gg$

$\Delta {G^\theta } = \ll - nF{E^\theta } = - 9.65 \times {10^4}{\text{ C}}\,{\text{mo}}{{\text{l}}^{ - 1}} \times 0.60{\text{ J}}\,{{\text{C}}^{ - 1}} = \gg - 57\,900{\text{ }}\ll {\text{J}}\,{\text{mo}}{{\text{l}}^{ - 1}}\gg / - 57.9{\text{ }}\ll {\text{kJ}}\,{\text{mo}}{{\text{l}}^{ - 1}}\gg$