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

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

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

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

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.

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

Do not penalize incorrect notation twice.

[2 marks]

H₂SO₃(aq)
OR
Pb(s)

[1 mark]

Zn(s)

[1 mark]

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

Accept equilibrium sign.

[1 mark]

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

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

spontaneous as \(\Delta {G^\theta }\) is negative

Do not award M3 as a stand-alone answer.

Accept “spontaneous” for M3 if answer given for M2 is negative.

Accept “spontaneous as \({E^\theta }\) is positive” for M3.

[3 marks]