Chemistry · Chemistry of the atmosphere. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
The air today is about four-fifths nitrogen and one-fifth oxygen, with small amounts of other gases. It has been much the same for about 200 million years, but the early atmosphere was very different.
One theory says that intense volcanic activity in the first billion years released the early atmosphere. It was mostly carbon dioxide, with little or no oxygen, like Mars and Venus today. Water vapour condensed to form the oceans as the Earth cooled.
Later, algae and then plants made oxygen by photosynthesis. Carbon dioxide fell because it was used in photosynthesis, dissolved in the oceans, and was locked up in sedimentary rocks and fossil fuels.
Students say that volcanoes released the oxygen in the air. Volcanoes gave carbon dioxide, water vapour and nitrogen; the oxygen came later from photosynthesis by algae and plants.
Answer: 64 g of oxygen.
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