Chemical cells and fuel cells (chemistry only) exam tips

Exam tips

• Focus on Electrode Roles

  When writing the hydrogen half‑equation, first identify the electrode type (anode or cathode) and the direction of electron flow. Remember that in a hydrogen fuel cell the hydrogen electrode is the anode where oxidation occurs, so electrons are produced and leave the electrode.

  Clarifying the electrode role prevents confusion between oxidation and reduction steps, ensuring the correct sign for electrons and the proper placement of the half‑equation in the overall reaction.

• Mastering Half Equations

  Explain clearly: Explain practice writing half equations for both the hydrogen and oxygen reactions in a hydrogen fuel cell to reinforce your understanding. Link your answer to Fuel cells in Chemical cells and fuel cells (chemistry only); for bond-energy work, separate bonds broken from bonds formed and include the sign and unit.

  This helps you grasp the electrochemical processes involved and prepares you for questions requiring detailed knowledge of reactions. This prevents Unit 4.5 mistakes such as confusing exothermic with endothermic, activation energy with overall energy change, or fuel-cell reactions with rechargeable cells.

• Understand Half Equations

  Practice writing and linking half equations for hydrogen and oxygen in fuel cells to the overall reaction producing water.

  This helps you grasp the electrochemical processes in fuel cells, essential for linking half equations to the overall reaction.