To determine the empirical formula and molecular formula for methyl salicylate, we need to first calculate the empirical formula using the given mass percent composition.
Step 1: Convert the mass percent composition to grams.
Given:
Mass percent of C = 63.2%
Mass percent of O = 31.6%
Mass percent of H = 5.26%
To convert the mass percent to grams, assume that we have a 100g sample.
Mass of C = (63.2/100) x 100g = 63.2g
Mass of O = (31.6/100) x 100g = 31.6g
Mass of H = (5.26/100) x 100g = 5.26g
Step 2: Calculate the number of moles of each element.
To calculate the number of moles, we need to divide the mass of each element by its molar mass.
Molar mass of C = 12.01 g/mol
Molar mass of O = 16.00 g/mol
Molar mass of H = 1.01 g/mol
Number of moles of C = 63.2g / 12.01 g/mol = 5.268 mol
Number of moles of O = 31.6g / 16.00 g/mol = 1.975 mol
Number of moles of H = 5.26g / 1.01 g/mol = 5.204 mol
Step 3: Divide each number of moles by the smallest number of moles.
The empirical formula represents the simplest whole number ratio of elements in a compound. To find the empirical formula, divide each number of moles by the smallest number of moles.
For methyl salicylate, the smallest number of moles is 1.975 (from O).
Number of moles of C (rounded to the nearest whole number) = 5.268 / 1.975 ≈ 2.7
Number of moles of O (rounded to the nearest whole number) = 1.975 / 1.975 = 1
Number of moles of H (rounded to the nearest whole number) = 5.204 / 1.975 ≈ 2.6
Step 4: Write the empirical formula.
The empirical formula is written using the whole number ratio calculated in the previous step.
Empirical formula for methyl salicylate: C2.7O1H2.6
Step 5: Calculate the molecular formula.
To find the molecular formula, we need additional information - the mass of one molecule of the compound. Given that the mass of one molecule of methyl salicylate is 2.53 x 10^-22 g, we can compare the molar mass of the empirical formula with the molar mass of the molecular formula to find the ratio.
Molar mass of empirical formula = (2.7 x 12.01) + (1 x 16.00) + (2.6 x 1.01) = 60.0 g/mol (approximately)
Now, we calculate the ratio of the molar mass of the molecular formula to the molar mass of the empirical formula.
Ratio = (2.53 x 10^-22 g) / (60.0 g/mol)
By dividing the molecular mass by the empirical mass, we can find the number of empirical formula units per molecule.
Ratio (rounded to the nearest whole number) = (2.53 x 10^-22 g) / (60.0 g/mol) ≈ 4.2 x 10^-24
Finally, we multiply the subscripts of the empirical formula by the ratio to obtain the molecular formula:
Empirical formula: C2.7O1H2.6
Molecular formula: C11O4H10