The current “petrochemical economy” is based on the combustion of fossil fuels, of which liquid octane is a typical example:

C₈H₁₈(l) + 12.5 O₂(g)  →  8 CO₂(g) + 9 H₂O (l)

The so-called “hydrogen economy” is based on H₂(g) produced from water by solar energy. The gas is then burned as fuel:

2H₂(g) + O₂(g)  →  2H₂O(l)

1. A major disadvantage of hydrogen as a fuel is that it is a gas, and therefore harder to store. Calculate the volume of H₂ gas at 25 °C and 1 atm required to produce the same amount of heat as 1.00 L of liquid octane. (The density of liquid octane is 0.67 kg L^–1)

   

2. Rather than simply burning H₂(g), it can be used to produce an electric current using a fuel cell (pictured above). based on the diagram above, determine the half equations for this cell and thus the expected E° of the cell (note: A standard reduction table is provided in formula sheet). What would you expect to happen to the E of the cell if the pressure of O₂ was increased?

Type your answers to both parts a and b in the box below