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.
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To find the empirical formula of ascorbic acid, we need to determine the ratio of carbon (C) and hydrogen (H) atoms in the compound.
1. Find the number of moles of CO2:
- Mass of CO2 = 1.5 g
- Molecular weight of CO2 = 44 g/mol
- Moles of CO2 = Mass of CO2 / Molecular weight of CO2
2. Find the number of moles of H2O:
- Mass of H2O = 0.409 g
- Molecular weight of H2O = 18 g/mol
- Moles of H2O = Mass of H2O / Molecular weight of H2O
3. Determine the ratio of C to H:
- Each mole of CO2 contains 1 mole of C atoms.
- Each mole of H2O contains 2 moles of H atoms.
Divide the number of moles of H2O by 2 and compare it to the number of moles of CO2. This will give you the ratio of H to C atoms.
4. Determine the empirical formula using the ratio of C to H:
- The empirical formula gives the simplest whole-number ratio of atoms in the compound. If the ratio of C to H is 1:2, the empirical formula will be CHO. If the ratio is 2:4, the empirical formula will be C2H4O2. If the ratio is 3:4, the empirical formula will be C3H4O3.
5. Compare the empirical formula possibilities to the choices given in the question:
- The possible empirical formulas are CHO, C2H4O2, and C3H4O3. Compare these options with the provided choices to determine the correct empirical formula of ascorbic acid.