Combustion Analysis

Combustion Analysis

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Ex - Find the empirical formula of vitamin C (ascorbic acid), a compound that contains only C, H, and O. Combustion of 1.000 g of vitamin C produced 1.500 g of CO2 and 0.405 g of H2O.

The general reaction is:CxHyOz + O2 CO2 + H2OSo, all of the carbon in the compound is incorporated into the carbon dioxide. We can take the 1.500 g of CO2 and determine the mass of carbon in it.

3All of the hydrogen is incorporated into the water. We can take the 0.405 g of water and calculate the amount of hydrogen it contains.

4Oxygen is added to the reaction so we must get the oxygen by subtraction from the mass of the original compound.1.000 g 0.4093 g C 0.0454 g H =0.5453 g O

Now we can do a regular empirical formula problem.CHO0.4093 g0.0454 g0.5453 gDivide by each atomic weight to get moles/ 12.01/ 1.01/16.00= 0.03408= 0.04495= 0.03408

Divide each by the smallest to find the whole number ratio./0.03408/.03408/.03408= 1= 1.32= 1Multiplying each by 3 will give whole numbers. The compound is then C3H4O3.

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