A compound contains 40.0% carbon 6.7% hydrogen and 53.3% oxygen. If the molar mass of the compound is 180, find the molecular formula. [H = 1, C = 12, O = 1...
A compound contains 40.0% carbon 6.7% hydrogen and 53.3% oxygen. If the molar mass of the compound is 180, find the molecular formula.
[H = 1, C = 12, O = 16]
Answer Details
First, we need to determine the empirical formula of the compound, which gives the simplest whole-number ratio of atoms in the compound. To do this, we assume that we have 100 g of the compound, which means we have 40.0 g of carbon, 6.7 g of hydrogen, and 53.3 g of oxygen.
Next, we convert these masses to moles by dividing by the respective atomic or molecular masses:
- Carbon: 40.0 g / 12.0 g/mol = 3.33 mol
- Hydrogen: 6.7 g / 1.0 g/mol = 6.7 mol
- Oxygen: 53.3 g / 16.0 g/mol = 3.33 mol
The mole ratio of these elements is approximately 1:2:1, which gives us the empirical formula CH2O.
To find the molecular formula, we need to know the molecular mass of the empirical formula. The molecular mass of CH2O is:
- Carbon: 1 x 12.0 g/mol = 12.0 g/mol
- Hydrogen: 2 x 1.0 g/mol = 2.0 g/mol
- Oxygen: 1 x 16.0 g/mol = 16.0 g/mol
Total: 30.0 g/mol
We are given that the molar mass of the compound is 180 g/mol. To find the molecular formula, we divide the molar mass by the empirical formula mass:
180 g/mol ÷ 30.0 g/mol = 6
The molecular formula is the empirical formula multiplied by the whole number 6:
6 x CH2O = C6H12O6.
Therefore, the molecular formula of the compound is C6H12O6.