- this is only counting carbon weight (12 amu) and does not include the additional weight of two oxygens (32 amu)
the weight of carbon needed to convert all that O2 to co2 would be:
(10^18)*(12/44) = 2.7*10^17 Kg
Other Answers (3)
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Much of the carbon is now trapped in limestone and other carbonates that were created by life in the sea. Today, corals and shellfish are creating more such carbonates. Trees and other plants only trap carbon for a short time, and then they die and decay and release the carbon dioxide back into the air. That is why planting trees does not help in the long run. But the lime stone and sea shells can last millions of years after the creature that made it is dead. Coral reefs are mountains of coral skeletons that have trapped in them lots of carbon.
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Oxygen can also come from photolysis of water in the upper atmosphere; the hydrogen then diffuses upward and can escape into space. This process would go much faster before there was an ozone layer to protect the lower atmosphere against UV.
It is believed that the water on Venus disappeared in this way. -
The free oxygen came from a plant that converted it from CO2, right? Well, what do you think that plant is made of? Carbon!
The biotic matter on the planet is an enormous carbon sink (which is what makes deforestation so concerning)
