Explain cryolite, electrode reactions and replacement of carbon anodes.
| English | Chinese |
|---|---|
| bauxite | 铝土矿 |
| cryolite | 冰晶石 |
| anode | 阳极 |
Try each question before opening its hint or answer. Use paper for calculations and diagrams.
Why is an aqueous solution unsuitable for producing aluminium at the cathode?
Identify the ion charge before adding electrons. Balance atoms and charge separately.
Hydrogen forms in preference to aluminium in an aqueous electrolyte. A molten electrolyte is used.
Give the purpose of cryolite.
Consider the melting point of pure aluminium oxide.
Cryolite lowers the operating temperature and therefore the energy required.
Write the oxide-ion half-equation and explain why the anode needs replacing.
Oxide ions lose electrons; the resulting gas reacts with carbon.
2O²⁻ → O₂ + 4e⁻. Oxygen reacts with the carbon anode, consuming it.
Use Lesson 3 in your worksheet for written practice. Your teacher will discuss those answers in class.