Posted by Jon on .
Combustion analysis of a 1.00g sample of ascorbic acid yields 1.500g of CO2 and 0.409g of H2O. What is the empirical formula of ascorbic acid?
(a. CHO B.CH2O C. C2H4O2 D. C3H4O3 E.Cannot be determined with the information given. )
Convert the 1.5 g of CO2 and 0.409 g of H20 by dividing by the molecular weights 44 and 18, respectively. Use the results to determine the C/H ratio in the ascorbic acid. Each mole of CO2 will Nav atoms of C and each mole of H2O will contain 2Nav atoms of H, where Nav is Avogadro's number. The ratio of the numbers of H and C atoms in the products must equal that in the ascorbic acid. You won't be able to get the amount of O in the empirical formula however, since you are adding it in excess to perform the combustion.
You can get the amount of O in the empirical formula by converting the total moles of H and C to masses and subtracting them from the 1.00g initial mass of the ascorbic acid. Convert this mass to moles, and you have moles of O to work with.