posted by hh on .
What is the empirical formula for menthol when a 0.1005g sample of menthol is combusted, producing 0.28298g of CO2 and 0.1159g of H2O.
Here an outline of the solution. The answers to the answers in each step should have at least four significant figure.
1. Convert the grams of CO2 and H2O to moles
2. Moles of carbon, C, equals the number of moles of CO2. Convert the moles of C to grams of C.
3. Moles of hydrogen, H, equal (1/2)(moles H2O). Convert moles of H to grams of H.
4. To get grams of oxygen, O, subtract the combined mass of C and H from the mass of the sample:
0.1005g - (grams C + grams H)
Convert the grams of oxygen, O to moles.
5. The formula for menthol is CxHyOz
x = moles of C
y = moles of H
z = moles of O
6. Divide x, y, and z by the smallest of the three values. The new set of values are the subscripts for the formula of menthol. With a little rounding off they should be whole numbers. If not, multiplication by a small whole number may produce the set of three subscripts needed.