Determining the Molecular Formula from Empirical and Molar Mass

Understanding the Concept

The molecular formula of a compound is determined based on both its empirical formula and molar mass. Understanding the relationship between these two can help in identifying the exact molecular structure of a compound. This article will guide you through the process of determining the molecular formula for a compound with a molar mass of 82 amu and an empirical formula of C3H5.

Calculating Molar Mass from Empirical Formula

Step 1: Calculate the Molar Mass of the Empirical Formula. Carbon (C): 12.01 g/mol × 3 36.03 g/mol Hydrogen (H): 1.008 g/mol × 5 5.04 g/mol Total molar mass of C3H5 36.03 g/mol 5.04 g/mol 41.07 g/mol

The molar mass of the empirical formula C3H5 is 41.07 g/mol.

Using Molar Mass to Find the Ratio

Step 2: Determine the Ratio. Given molar mass of the compound 82 amu (equivalent to 82 g/mol) Ratio 82 g/mol ÷ 41.07 g/mol ≈ 2

The ratio is approximately 2, indicating that the molecular formula is twice the empirical formula.

Multiplying the Subscripts

Step 3: Multiply the Subscripts by the Ratio. Empirical formula C3H5 Molecular formula C3×2H5×2 C6H10

Thus, the molecular formula for the compound is C6H10.

Conclusion

By following these steps, we can accurately determine the molecular formula of a compound given its empirical formula and molar mass. In the case of a compound with an empirical formula of C3H5 and a molar mass of 82 amu, the molecular formula is C6H10.

References and Further Reading

For more detailed information about molecular and empirical formulas, refer to chemical formula resources. Understanding the relationship between these formulas help in the accurate identification and interpretation of compound structures.