What are the two main gases that make up air?

  1. Nitrogen
  2. Oxygen

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How does this practical work to measure oxygen levels?

Iron filings react with the oxygen inside a sealed burette. As oxygen is used up, the volume of air decreases, allowing the oxygen content to be measured.

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Why are iron filings used in this practical?

Iron reacts with oxygen to form iron oxide (rust). This reaction allows the oxygen levels to be measured.

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Why is a burette used in this practical?

The burette allows accurate measurement of the change in gas volume, which corresponds to oxygen levels.

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Why are the iron filings made wet?

To allow the reaction between iron and oxygen to occur.

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What calculation is done to determine percentage oxygen?

Divide change in burette reading by original burette volume and multiply by 100.

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Is this practical measuring oxygen by mass or volume?

By volume.

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Over what time period is this practical conducted?

Over a few weeks.

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