The empirical formula of a chemical substance is CH2. The molar mass of a molecule of the substance is 56.108 g/mol. what is the molecular formula of the chemical substance? (4 points) c3h4 c4h8 c2h4 c6h6
The Correct Answer and Explanation is:
The problem provides the empirical formula ( \text{CH}_2 ) and the molar mass of the substance as ( 56.108 \, \text{g/mol} ). To determine the molecular formula, we need to follow these steps:
Step 1: Find the Molar Mass of the Empirical Formula
The empirical formula is ( \text{CH}_2 ), which consists of one carbon (C) atom and two hydrogen (H) atoms.
- The atomic mass of carbon (C) is approximately ( 12.01 \, \text{g/mol} ).
- The atomic mass of hydrogen (H) is approximately ( 1.008 \, \text{g/mol} ).
Thus, the molar mass of the empirical formula ( \text{CH}_2 ) is:
[
\text{Molar mass of CH}_2 = (12.01 \, \text{g/mol}) + (2 \times 1.008 \, \text{g/mol}) = 12.01 \, \text{g/mol} + 2.016 \, \text{g/mol} = 14.026 \, \text{g/mol}
]
Step 2: Determine the Ratio of the Molar Mass of the Molecular Formula to the Empirical Formula
Next, we divide the molar mass of the substance (given as ( 56.108 \, \text{g/mol} )) by the molar mass of the empirical formula (( 14.026 \, \text{g/mol} )):
[
\frac{\text{Molar mass of molecular formula}}{\text{Molar mass of empirical formula}} = \frac{56.108 \, \text{g/mol}}{14.026 \, \text{g/mol}} \approx 4
]
This means the molecular formula is four times the empirical formula.
Step 3: Multiply the Empirical Formula by the Ratio
Since the ratio is 4, we multiply the empirical formula ( \text{CH}_2 ) by 4:
[
\text{Molecular formula} = (\text{CH}_2) \times 4 = \text{C}_4\text{H}_8
]
Step 4: Conclusion
The molecular formula of the substance is ( \text{C}_4\text{H}_8 ). Therefore, the correct answer is C4H8.
Explanation Summary
The process to determine the molecular formula involves comparing the molar mass of the empirical formula with the given molar mass of the substance. By dividing the given molar mass by the empirical formula’s molar mass, we find the factor by which the empirical formula must be multiplied to obtain the molecular formula. In this case, the molecular formula is four times the empirical formula, resulting in ( \text{C}_4\text{H}_8 ).