What is the molecular formula of a molecule that has an empirical formula of CH2O and a molar mass of 120.12g/mol?
4(CH20)= C4H8O4
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To determine the molecular formula of a molecule given its empirical formula and molar mass, you need the molar mass of the empirical formula. In this case, the empirical formula is CH2O.
Step 1: Calculate the molar mass of the empirical formula.
The molar mass of carbon (C) is approximately 12.01 g/mol, the molar mass of hydrogen (H) is approximately 1.01 g/mol, and the molar mass of oxygen (O) is approximately 16.00 g/mol. To calculate the molar mass of the empirical formula (CH2O), we add together the molar masses of each element:
(1 × 12.01 g/mol) + (2 × 1.01 g/mol) + (1 × 16.00 g/mol) = 12.01 g/mol + 2.02 g/mol + 16.00 g/mol = 30.03 g/mol.
Step 2: Calculate the ratio between the molar masses.
Divide the given molar mass of 120.12 g/mol by the molar mass of the empirical formula (30.03 g/mol):
120.12 g/mol ÷ 30.03 g/mol = 4.
Step 3: Determine the molecular formula.
The ratio calculated in step 2 represents the number of empirical formulas within the molecular formula. Therefore, the molecular formula will be four times (4 ×) the empirical formula:
C4H8O4.
Therefore, the molecular formula of the molecule is C4H8O4.
To find the molecular formula of a compound given its empirical formula and molar mass, we need to determine the ratio between the empirical formula mass and the molar mass.
1. Calculate the empirical formula mass:
- The empirical formula for the compound is CH2O.
- The atomic mass of carbon (C) is approximately 12.01 g/mol.
- The atomic mass of hydrogen (H) is approximately 1.01 g/mol.
- The atomic mass of oxygen (O) is approximately 16.00 g/mol.
( C: 12.01 g/mol ) + ( H: 1.01 g/mol × 2 ) + ( O: 16.00 g/mol ) = 30.03 g/mol
2. Determine the ratio between the empirical formula mass and the molar mass:
- Divide the molar mass by the empirical formula mass:
120.12 g/mol ÷ 30.03 g/mol ≈ 4
This means that the molar mass is approximately four times greater than the empirical formula mass.
3. Multiply the subscripts in the empirical formula by the ratio obtained in Step 2:
- Empirical formula: CH2O
- Multiply the subscripts by 4: (C4H8O4).
The molecular formula of the compound is C4H8O4.