The molecular formula for octane is C8H18. Calculate the molar mass of the empirical formula of octane. 114.432 g/mol 228.464 g/mol 57.116 g/mol 14.279 g/mol
The Correct Answer and Explanation is:
To determine the molar mass of the empirical formula of octane (C8H18), we first need to find the empirical formula itself. The empirical formula represents the simplest whole-number ratio of the elements in a compound.
Step 1: Determine the empirical formula of octane
Octane’s molecular formula is C8H18, which shows there are 8 carbon (C) atoms and 18 hydrogen (H) atoms. To find the empirical formula, we divide both the number of carbon atoms and the number of hydrogen atoms by their greatest common divisor (GCD).
The GCD of 8 and 18 is 2.
Thus, divide the subscripts of both elements by 2:
- Carbon (C): 8 / 2 = 4
- Hydrogen (H): 18 / 2 = 9
Therefore, the empirical formula of octane is C4H9.
Step 2: Calculate the molar mass of the empirical formula (C4H9)
To find the molar mass, we sum the atomic masses of the elements in the empirical formula:
- The atomic mass of carbon (C) is 12.01 g/mol.
- The atomic mass of hydrogen (H) is 1.008 g/mol.
So, the molar mass of C4H9 is calculated as:
- 4 carbon atoms × 12.01 g/mol = 48.04 g/mol
- 9 hydrogen atoms × 1.008 g/mol = 9.072 g/mol
Total molar mass = 48.04 g/mol + 9.072 g/mol = 57.112 g/mol
Step 3: Answer
The molar mass of the empirical formula of octane (C4H9) is approximately 57.116 g/mol. Thus, the correct answer is:
57.116 g/mol
Conclusion
The empirical formula of a compound represents its simplest form, which helps simplify the calculation of molar masses. The molecular formula of octane (C8H18) corresponds to a more complex version of this empirical formula, but the molar mass of the empirical formula C4H9 is about 57.116 g/mol.
