SSCE VCE Chemistry Primary Galvanic Cells and Fuel Cells as Sources of Energy: A vanadium redox battery is used

Question

A vanadium redox battery is used to store electrical energy generated at a wind farm in Tasmania. The battery supplies electricity to the power grid as required through a control switch.

The diagram below shows the structure of a cell in a vanadium redox battery. The reactants are dissolved in an acidic solution, stored in large tanks and pumped through the cell. The cell is recharged using electricity generated by the wind turbines. A polymer membrane allows the movement of particular ions.

The two relevant half-equations for the vanadium redox battery are

$$	ext{VO}_2^+(aq) + 2	ext{H}^+(aq) + e^- \leftrightarrow 	ext{VO}_2^+(aq) + 	ext{H}_2O(l) \quad E^\circ = +1.004 	ext{ V}$$

$$	ext{V}^{3+}(aq) + e^- \leftrightarrow 	ext{V}^{2+}(aq) \quad E^\circ = -0.255 	ext{ V}$$

a. State the polarity of each electrode as the battery is discharged.

Electrode A  
Electrode B

b. Circle the vanadium-containing ion that would have the highest concentration at the anode when the cell is fully charged.

VO$_2^+$  
VO$^+$  
V$^{3+}$  
V$^{2+}$

c. Write a balanced overall equation for the reaction that occurs when the cell is being recharged.

d. Compare the vanadium redox cell to a fuel cell by describing one major way in which they differ.

e. Write a balanced overall equation to show why iron would be an unsuitable material to use as electrode B in the vanadium redox cell.

A vanadium redox battery is used to store electrical energy generated at a wind farm in Tasmania - VCE - SSCE Chemistry - Question 5 - 2009 - Paper 1

Worked Solution & Example Answer:A vanadium redox battery is used to store electrical energy generated at a wind farm in Tasmania - VCE - SSCE Chemistry - Question 5 - 2009 - Paper 1

a. State the polarity of each electrode as the battery is discharged.

b. Circle the vanadium-containing ion that would have the highest concentration at the anode when the cell is fully charged.

c. Write a balanced overall equation for the reaction that occurs when the cell is being recharged.

d. Compare the vanadium redox cell to a fuel cell by describing one major way in which they differ.

e. Write a balanced overall equation to show why iron would be an unsuitable material to use as electrode B in the vanadium redox cell.

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