A compound isolated from oil of mint has a characteristic cool, refreshing odour. It is frequently used in cough drops to ease the pain of a sore throat. This compound contains only C, H, and O. If 95.6 mg of this compound burns completely in O2, and yields 269 mg of CO2 and 111 mg of H2O, find the empirical formula of the compound.
Compound + O2(g) --> CO2(g) + H2O(g)
To determine the empirical formula of the compound, we need to find the ratio of the number of moles of each element present in the compound.
1. Start by converting the given masses of CO2 and H2O into moles.
The molar mass of CO2 (carbon dioxide) is 44.01 g/mol.
Number of moles of CO2 = mass of CO2 / molar mass of CO2
Number of moles of CO2 = 269 mg / 44.01 g/mol = 0.00611 mol
The molar mass of H2O (water) is 18.02 g/mol.
Number of moles of H2O = mass of H2O / molar mass of H2O
Number of moles of H2O = 111 mg / 18.02 g/mol = 0.00616 mol
2. Determine the number of moles of carbon (C), hydrogen (H), and oxygen (O) present in the compound.
Since CO2 has one carbon atom and H2O has no carbon atoms, the number of moles of carbon (C) can be determined from the number of moles of CO2.
Number of moles of C = 0.00611 mol
Since H2O has two hydrogen atoms, the number of moles of hydrogen (H) can be determined.
Number of moles of H = 2 * 0.00616 mol = 0.01232 mol
The remaining moles are attributed to oxygen (O).
Number of moles of O = total number of moles - (number of moles of C + number of moles of H)
Number of moles of O = 0.00611 + 0.01232 = 0.01843 mol
3. Find the empirical formula by dividing each number of moles by the smallest number of moles obtained.
Divide the number of moles of each element by the smallest number of moles, which is 0.00611 mol in this case.
C: 0.00611 mol / 0.00611 mol = 1
H: 0.01232 mol / 0.00611 mol = 2
O: 0.01843 mol / 0.00611 mol = 3
The empirical formula of the compound is C1H2O3.