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Assigning Oxidation Numbers

Introduces oxidation numbers and describes how to determine them.

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Practice Assigning Oxidation Numbers
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Cleaning Things Up

Cleaning Things Up

Credit: Adam Jenkins
Source: http://www.flickr.com/photos/37796451@N00/4871934432
License: CC BY-NC 3.0

Got an old computer you don’t need any more? You can’t just throw it out – the Environmental Protection Agency (EPA) has classified them as hazardous waste and subject to EPA regulations regarding disposal of such materials. It’s not useful as a computer anymore, because it was probably obsolete six months after you bought it. One possibility is to recycle the system, allowing recovery of several materials and avoidance of landfill or atmospheric contamination.

News You Can Use

  • Metals play indispensable roles in our daily lives. We use computers that contain a number of different metals. We wear gold and silver jewelry. Watch cases may be made of gold, silver, or platinum and contain batteries whose contents would be considered as environmental hazards. Metals such as iron and aluminum are widely employed in construction as well as a multitude of everyday uses.
  • Whether the metal comes to us mined from the Earth or as a recycled component, oxidation-reduction processes are needed to purify the metal for the first time or to recover the metal so it can be used again. Often the raw material is a metal compound (such as aluminum or iron oxide) that needs to be reduced to the metallic form.
  • Credit: Peter Craven
    Source: http://www.flickr.com/photos/cdeimages/6024890677/
    License: CC BY-NC 3.0

    Iron is mined in the form of iron ore, which must be processed before it becomes metallic iron [Figure2]


  • Several techniques are available for purification of metals. Low-melting metals can be heated and separated from still-solid impurities. Mercury can be distilled since it has a low boiling point. Passage of oxygen through the metal will remove some impurities that form gaseous oxides. Electric current can be employed to reduce ionic forms of metals to their pure metallic forms.
  • Watch a video about recycling metals from computers at the link below:


Show What You Know

Use the links below to learn more about metal refining. Then answer the following questions.

  1. What metals can be purified by liquation?
  2. What is the Hall-Heroult process for aluminum refining?
  3. What was smelting of iron ore?
  4. How much silver would be in a typical ore?

Image Attributions

  1. [1]^ Credit: Adam Jenkins; Source: http://www.flickr.com/photos/37796451@N00/4871934432; License: CC BY-NC 3.0
  2. [2]^ Credit: Peter Craven; Source: http://www.flickr.com/photos/cdeimages/6024890677/; License: CC BY-NC 3.0

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