To determine the molecular formula of a compound given its empirical formula and molar mass, you can follow these steps:
1. Identify the elements and their atomic masses in the empirical formula:
- The empirical formula is OH.
- The atomic mass of Oxygen (O) is approximately 16 g/mol.
- The atomic mass of Hydrogen (H) is approximately 1 g/mol.
2. Calculate the mass of the empirical formula:
- The mass of OH = mass of O + mass of H = 16 g/mol + 1 g/mol = 17 g/mol.
3. Determine the ratio of the molar mass of the compound to the mass of the empirical formula:
- Given the molar mass of the compound is 30 g/mol.
- Ratio [tex]\(n\)[/tex] = [tex]\(\frac{\text{Molar mass of the compound}}{\text{Mass of the empirical formula}}\)[/tex]
[tex]\[
n = \frac{30 \text{ g/mol}}{17 \text{ g/mol}} \approx 1.76
\][/tex]
4. Interpret the result:
- Since the ratio [tex]\(n\)[/tex] is close to an integer, we usually round it to the nearest whole number. In this case, 1.76 rounds to 2.
5. Multiply the subscripts in the empirical formula by this ratio to get the molecular formula:
- Subscripts in OH are 1 for both O and H.
- Multiplying each subscript by 2 (the rounded ratio):
- Oxygen: [tex]\(1 \times 2 = 2\)[/tex]
- Hydrogen: [tex]\(1 \times 2 = 2\)[/tex]
6. Write the molecular formula:
- The molecular formula is [tex]\(O_2H_2\)[/tex].
- Simplified, this is usually written as [tex]\(H_2O_2\)[/tex] (Hydrogen Peroxide).
Therefore, the molecular formula of the compound whose empirical formula is OH and whose molar mass is 30 g/mol is [tex]\(H_2O_2\)[/tex].
