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The compound ascorbic acid (vitamin C) is a carbon-hydrogen-oxygen compound. This water-soluble vitamin cannot be stored in the body and thus must continuously be supplied by the diet. Combustion analysis of a 3.08 g ascorbic acid sample yields 6.17 g of CO2 and 2.52 g of H2O. What is the empirical formula for ascorbic acid?
Solution:
Since the molecule of ascorbic acid consists of carbon, hydrogen, and oxygen atoms, then we need to get the weight of each atoms first as follows:
Weight of carbon in a sample is
Weight of hydrogen in a sample is
Weight of oxygen in a sample is
Next, we need to get the number of moles of each atoms in a sample as follows:
Moles of carbon in a sample is
Moles of hydrogen in a sample is
Moles of oxygen in a sample is
From the number of moles of each component, we need to divide all of them by their least number of moles which is oxygen in order to get the number of atoms in a sample.
Number of carbon in a sample is
Number of hydrogen in a sample is
Number of oxygen in a sample is
Therefore, the empirical formula of ascorbic acid (vitamin C) is
