An unknown compound contains 13.04% of hydrogen,34.78% of oxygen, and 52.17% of carbon by mass. Determine the empirical formula of the unknown compound. (Atomic massof O-15.999 g/mol; H-1.008 g/mol; C-12.011 g/mol)
CH2OH
C2H6O
C2H6OH
C6H12O6
To find the empirical formula, we need to determine the simplest whole number ratio of atoms in the compound.
1. Convert the mass percentage of each element to mass:
- Hydrogen: 13.04% of the total mass = 13.04 g (since we can assume a 100g sample)
- Oxygen: 34.78% of the total mass = 34.78 g
- Carbon: 52.17% of the total mass = 52.17 g
2. Convert the mass of each element to moles using their atomic mass (in g/mol):
- Hydrogen: 13.04 g ÷ 1.008 g/mol = 12.94 mol
- Oxygen: 34.78 g ÷ 15.999 g/mol = 2.17 mol
- Carbon: 52.17 g ÷ 12.011 g/mol = 4.34 mol
3. Find the simplest whole number ratio of moles by dividing each value by the smallest mole value:
- Hydrogen: 12.94 mol ÷ 2.17 mol = 5.96 ≈ 6
- Oxygen: 2.17 mol ÷ 2.17 mol = 1
- Carbon: 4.34 mol ÷ 2.17 mol = 2
4. Write the empirical formula using the whole number ratio of atoms:
C2H6O
Therefore, the empirical formula of the unknown compound is C2H6O.
To determine the empirical formula of the unknown compound, we need to find the simplest whole number ratio of the elements present.
Step 1: Convert the percentages to grams.
Given:
Mass of Hydrogen (H) = 13.04% = 13.04 grams
Mass of Oxygen (O) = 34.78% = 34.78 grams
Mass of Carbon (C) = 52.17% = 52.17 grams
Step 2: Convert the grams to moles using the atomic masses.
Molar mass of Hydrogen (H) = 1.008 g/mol
Molar mass of Oxygen (O) = 15.999 g/mol
Molar mass of Carbon (C) = 12.011 g/mol
Number of moles of Hydrogen (H) = 13.04 g / 1.008 g/mol = 12.92 mol
Number of moles of Oxygen (O) = 34.78 g / 15.999 g/mol = 2.18 mol
Number of moles of Carbon (C) = 52.17 g / 12.011 g/mol = 4.34 mol
Step 3: Divide the number of moles by the smallest number of moles to obtain the simplest ratio.
Dividing all the values by the smallest number of moles (2.18 mol):
H: 12.92 mol / 2.18 mol = 5.94
O: 2.18 mol / 2.18 mol = 1
C: 4.34 mol / 2.18 mol = 2
Therefore, the empirical formula of the unknown compound is C2H6O.