1.1. In a hydrogen fuel cell, the reaction between hydrogen and oxygen produces electrical energy. The equation for the reaction is:

2H₂   +   O₂   →   2H₂O

Hydrogen fuel cells can be used to power some cars.

Reactions happen at both the positive electrode and the negative electrode in the fuel cell.

Write the two half equations that occur at each electrode and state with reason what kind of reaction each one is.

1.2. The energy required for a car powered by a hydrogen fuel cell to travel 400 km is 232 MJ.

The energy that is released when 1 mole of hydrogen gas reacts with oxygen is 290 kJ.

The volume of 1 mole of a gas at room temperature and pressure is 24 dm³.

Calculate the volume of hydrogen gas, in dm³, at room temperature and pressure needed for the car to travel 250 km.

1.3. The volume of hydrogen gas that would be required to allow a car to travel a reasonable distance between refuelling would be greater than the volume of a tank that could fit in a car.

Suggest one way in which this volume can be decreased.

1.4. Methanol can be used as the fuel in a fuel cell instead of hydrogen.

The chemical equation for is:

2CH₃OH + 3O₂ → 2CO₂ + 4H₂O

The equation for the reaction can be also be shown as:

Table 1 shows the bond energies of different bonds.

Table 1

The overall energy change for the reaction is -1318 kJ/mol.

Use the bond energies in Table 1 and the overall energy change to calculate the bond energy of the O=O bond in kJ/mol.