SSCE VCE Chemistry Redox Reactions: Hydrogen gas is an energy source

Question

Hydrogen gas is an energy source. Researchers are investigating the production of hydrogen gas in a microbial electrolysis cell.
The cell is made up of an anode half-cell and a cathode half-cell. The half-cells are separated by a proton exchange membrane, as shown in the diagram below.

A number of reactions take place in the cell, resulting in the production of hydrogen. These reactions are summarised below.

Anode half-cell
- The anode half-cell contains moist plant matter and electrochemically active bacteria that live on an inert anode.
- The gaseous mixture that is present in the half-cell does not contain oxygen.
- The moist plant matter ferments to produce ethanol acid (CH3COOH). Bacteria on the anode consume the ethanol acid and release hydrogen ions, electrons and carbon dioxide gas. A small voltage is then applied to reduce the H+ ions.

Cathode half-cell
- The cathode half-cell contains an inert cathode.
- The gaseous mixture that is present in the half-cell does not contain oxygen.
- The released hydrogen ions and electrons react to form hydrogen gas, as shown in the equation below.

2H+(aq) + 2e− → H2(g)

a. Ethanoic acid is converted to carbon dioxide gas and H+ ions at the anode. 
Write an equation for this reaction.

b. On the diagram above, use one arrow to indicate the direction of electron flow in the cell when an external voltage is applied to the cell by the power supply.

Hydrogen gas is an energy source - VCE - SSCE Chemistry - Question 7 - 2012 - Paper 1

Worked Solution & Example Answer:Hydrogen gas is an energy source - VCE - SSCE Chemistry - Question 7 - 2012 - Paper 1

a. Ethanoic acid is converted to carbon dioxide gas and H+ ions at the anode.

b. On the diagram above, use one arrow to indicate the direction of electron flow in the cell when an external voltage is applied to the cell by the power supply.

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