If the empirical formula is C3H3O and the molar mass is 110 g/mol, what is the molecular formula? A. C6H6O2 B. C9H9O3 C. C12H12O4 D. C15H15O5
The Correct Answer and Explanation is :
To determine the molecular formula, we need to compare the empirical formula to the molar mass given. The empirical formula is the simplest whole-number ratio of the elements in the compound, and the molecular formula is the actual number of atoms of each element in the compound.
Step 1: Calculate the molar mass of the empirical formula.
The empirical formula is C₃H₃O. To find its molar mass, we sum the atomic masses of each element in the empirical formula:
- Carbon (C) has an atomic mass of approximately 12 g/mol.
- Hydrogen (H) has an atomic mass of approximately 1 g/mol.
- Oxygen (O) has an atomic mass of approximately 16 g/mol.
Thus, the molar mass of C₃H₃O is:
[
3 \times 12 \, \text{g/mol} + 3 \times 1 \, \text{g/mol} + 1 \times 16 \, \text{g/mol} = 36 + 3 + 16 = 55 \, \text{g/mol}
]
So, the molar mass of the empirical formula is 55 g/mol.
Step 2: Compare the molar mass of the empirical formula to the given molar mass.
The problem gives the molar mass as 110 g/mol. To find how many times the empirical formula fits into the molecular formula, divide the molar mass of the molecular compound by the molar mass of the empirical formula:
[
\frac{110 \, \text{g/mol}}{55 \, \text{g/mol}} = 2
]
This means that the molecular formula is twice the empirical formula.
Step 3: Multiply the empirical formula by 2.
To obtain the molecular formula, multiply each element in the empirical formula by 2:
- Carbon: ( 3 \times 2 = 6 )
- Hydrogen: ( 3 \times 2 = 6 )
- Oxygen: ( 1 \times 2 = 2 )
Thus, the molecular formula is C₆H₆O₂.
Step 4: Identify the correct answer.
The molecular formula C₆H₆O₂ corresponds to option A.
Final Answer:
The correct answer is A. C₆H₆O₂.