Why is carbon used in the extraction of Aluminium?

Aluminium is too high in the electrochemical series (reactivity series) to extract it from its ore using carbon reduction. The temperatures needed are too high to be economic. Instead, it is extracted by electrolysis. The aluminium oxide has too high a melting point to electrolyse on its own.
A.

Why do you have to use electrolysis to extract Aluminium?

The method used to extract metals from the ore in which they are found depends on their reactivity. For example, reactive metals such as aluminium are extracted by electrolysis, while a less-reactive metal such as iron may be extracted by reduction with carbon or carbon monoxide.
  • Why does aluminum conduct electricity?

    For example, copper is used for electrical wiring because it is a good conductor of electricity. Metal particles are held together by strong metallic bonds, which is why they have high melting and boiling points. The free electrons in metals can move through the metal, allowing metals to conduct electricity.
  • Why gold is so expensive?

    Gold is relatively rare in the earth's crust, and particularly because of its value in making jewelry, it has always been worth a lot of money. Aluminum is very common, and is nowadays, easily formed as the pure metal, so it is not very cheap.
  • Why is aluminum ductile?

    The metallic bond is the force of attraction between these free electrons and metal ions. Metals are good conductors of electricity and heat, because the free electrons carry a charge or heat energy through the metal. The free electrons allow metal atoms to slide over each other, so metals are malleable and ductile.
B.

Why does the anode need to be replaced?

During the electrolysis process, aluminium is deposited at the cathode and oxygen is liberated at the anode. Some of this oxygen reacts with the carbon in the graphite to form carbon-dioxide, thus slowly burning away the anodes. Thus, the anodes have to replaced periodically.
  • Why do we recycle aluminum cans?

    Recycling aluminium uses only around 5% of the energy and emissions needed to make it from the raw material bauxite. The metal can be recycled time and time again without loss of properties, so getting the aluminium recycling habit is one of the best things we can do for the environment.
  • What is cryolite used for and why?

    The difficulty of separating aluminium from oxygen in the oxide ores was overcome by the use of cryolite as a flux to dissolve the oxide mineral(s). As natural cryolite is too rare to be used for this purpose, synthetic sodium aluminium fluoride is produced from the common mineral fluorite.
  • What is the inert electrode?

    Inert electrode is an electrode that serves only as a source or sink for electrons without playing a chemical role in the electrode reaction. Precious metals, mercury, and carbon are typically used as inert electrodes.
C.

Why are carbon anodes replaced regularly in the industrial electrolysis of Aluminium oxide?

The use of cryolite reduces some of the energy costs involved in extracting aluminium. The diagram shows an aluminium oxide electrolysis tank. Both the negative electrode (cathode) and positive electrode (anode) are made of graphite, a form of carbon. As a result, the positive electrodes have to be replaced frequently.
  • Why is aluminum used to make food containers?

    Aluminum foil provides a complete barrier to light, oxygen, moisture and bacteria. For this reason, foil is used extensively in food and pharmaceutical packaging. It is also used to make aseptic packaging that enables storage of perishable goods without refrigeration.
  • Why is aluminum ductile?

    The metallic bond is the force of attraction between these free electrons and metal ions. Metals are good conductors of electricity and heat, because the free electrons carry a charge or heat energy through the metal. The free electrons allow metal atoms to slide over each other, so metals are malleable and ductile.
  • Why do aluminum ions move to the negative electrode?

    Metal ions are positively charged, so metals are produced at the negative electrode (cathode). Negatively charged ions move to the positive electrode. Non-metal ions, such as oxide ions and chloride ions, are negatively charged, so gases such as oxygen or chlorine are produced at the positive electrode (anode).

Updated: 11th October 2018

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