What is the molecular formula of a compound with the empirical formula CH2 if the molecular mass of the compound is 56.10 g/mol?
The correct answer and explanation is :
To determine the molecular formula of a compound from its empirical formula and molecular mass, we can follow these steps:
Step 1: Calculate the molar mass of the empirical formula.
The empirical formula is CH₂, so we need to find its molar mass by summing the atomic masses of carbon (C) and hydrogen (H):
- Carbon (C) has an atomic mass of approximately 12.01 g/mol.
- Hydrogen (H) has an atomic mass of approximately 1.008 g/mol.
For the empirical formula CH₂:
- Molar mass = (1 × 12.01 g/mol) + (2 × 1.008 g/mol) = 12.01 g/mol + 2.016 g/mol = 14.026 g/mol.
Step 2: Determine the ratio of the molecular mass to the empirical formula mass.
The molecular mass of the compound is given as 56.10 g/mol. Now, we calculate the ratio of the molecular mass to the empirical formula mass:
- Ratio = Molecular mass / Empirical formula mass
- Ratio = 56.10 g/mol / 14.026 g/mol ≈ 4.
Step 3: Find the molecular formula.
The ratio tells us that the molecular formula is 4 times the empirical formula. Therefore, to get the molecular formula, multiply each element in the empirical formula by 4:
- Empirical formula: CH₂
- Molecular formula: (CH₂)₄ = C₄H₈.
Conclusion:
The molecular formula of the compound with the empirical formula CH₂ and a molecular mass of 56.10 g/mol is C₄H₈.
Explanation:
The empirical formula represents the simplest whole-number ratio of atoms in a compound. In this case, the empirical formula CH₂ suggests a ratio of 1 carbon atom to 2 hydrogen atoms. The molecular formula represents the actual number of atoms in the compound, which can be a multiple of the empirical formula. By comparing the molecular mass to the empirical formula mass, we find that the molecular formula is a multiple (in this case, 4) of the empirical formula. Therefore, the molecular formula is C₄H₈.