How are carbon and hydrogen of an organic compound estimated?

Explanation

A known weight of the organic compound is taken and completely burnt in excess of air and copper (II) oxide. Then carbon oxidises to `CO_(2)` and hydrogen oxidises to `H_(2)O`. The `CO_(2)` and `H_(2)O` so obtained are passed through already weighed U tubes containing anhydrous `CaCl_(2)` and caustic potash respectively. The increased weights of these two tubes give the weights of `H_(2)O` and `CO_(2)` formed.
Suppose that 'a'g of organic compound on combustion gives 'b' g of water vapour and 'c'g of `CO_(2)`.
% of carbon:
44 g of `CO_(2)` contains 12 g of carbon.
`therefore` 'c'g of `CO_(2)` contains . ..?
`=(12xxc)/44` g of carbon
'a' g of organic compound contains `(12xxc)/44`
g of carbon `therefore` 100 organic compound contains ………………. ?
`= (100 xx 12 xx c)/(a xx 44)` g of carbon (% of C)
% of hydrogen :
18 g of water contains 2 g of `H_(2)`
`therefore ` b of water contains …………… ?
`= (b xx 2)/(18)` g of hydrogen
a g of organic compounds contains `(b xx 2)/(18)` g of hydrogen .
`therefore` 100 g of organic compound contains ........... ?
`= (b xx 2 xx 100)/(18 xx a)` g of hydrogen (% of H)