Chemical quantities (AS)
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2 g of a particular organic compound was completely burnt in a plentiful supply of air. On analysis of the products of combustion, it was found that 2.74 g of carbon dioxide and 2.24 g of water were formed, with no other products.
How do you calculate the percentage by mass of carbon and hydrogen in this organic compound?
What other element must have been present?
Corrie writes...
The fraction of CO2 that is carbon is 12/44. Using this you can work out the mass of C in 2.74 g of CO2.
Similarly the fraction of H2O that is hydrogen is 2/18. Using this you can work out the mass of H in 2.24 g of water.
From these masses and the total mass you can work out the % of C and H in the organic compound.
The other element is most likely oxygen, as no products of combustion other than carbon dioxide and water are formed.
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updated: 14 October 2007
