Question

A 7.132 gram sample of an organic compound containing only C, H, and O is analyzed by combustion analysis and 11.88 g CO₂ and

3.891 g H₂0 are produced.
In a separate experiment, the molar mass is found to be 132.1 g/mol. Determine the empirical formula and the molecular formula
of the organic compound.

Answer 1

11 * CH₂ = C₁₁H₂₂

Step-by-step explanation:

The empirical formula of a compound can be determined by finding the ratio of the number of atoms of each element present in the compound. To find the empirical formula of this organic compound, we need to calculate the number of moles of each element present in the sample.

First, we find the number of moles of carbon by dividing the mass of CO₂ produced by the molar mass of CO₂:

11.88 g CO₂ / 44.01 g/mol CO₂ = 0.269 mol C

Next, we find the number of moles of hydrogen by dividing the mass of H₂O produced by the molar mass of H₂O:

3.891 g H₂O / 18.02 g/mol H₂O = 0.216 mol H

To find the empirical formula, we divide the number of moles of each element by the smallest number of moles calculated:

0.269 mol C / 0.216 mol H = 1.244

0.216 mol H / 0.216 mol H = 1

So the empirical formula of the organic compound is CH₂.

The molecular formula of a compound is a multiple of its empirical formula, with the multiple determined by the molar mass. To find the molecular formula of this organic compound, we divide the molar mass of the sample by the molar mass of the empirical formula:

132.1 g/mol / (12.01 g/mol + 2 * 1.01 g/mol) = 11

So the molecular formula of the organic compound is 11 * CH₂ = C₁₁H₂₂.



ALLEN

Answer 2

C4H8O4

Step-by-step explanation:

The empirical formula of a compound can be determined from its elemental composition. To determine the empirical formula, we first need to convert the mass of each element to moles, and then divide by the smallest number of moles of any element to obtain the mole ratio.

From the combustion analysis, the number of moles of CO₂ produced is 11.88 g / 44.01 g/mol = 0.2694 mol. The number of moles of H₂O produced is 3.891 g / 18.015 g/mol = 0.2169 mol.

Next, we convert the carbon and hydrogen present in the compound to moles by dividing the mass of each element by its atomic mass:

C = (7.132 g - 11.88 g - 3.891 g) / 12.01 g/mol = 0.2694 mol

H = 2 * 0.2169 mol = 0.4338 mol

Now, we divide each number of moles by the smallest number of moles (0.2694 mol) to obtain the mole ratio:

C = 0.2694 mol / 0.2694 mol = 1

H = 0.4338 mol / 0.2694 mol = 1.6

O = 0.2694 mol / 0.2694 mol = 1

The empirical formula of the compound is therefore C1H1.6O1, which can be simplified to C1H2O.

To determine the molecular formula, we use the molar mass of the compound, 132.1 g/mol, and compare it to the molar mass calculated from the empirical formula. The molar mass of C1H2O is 12.01 g/mol + 2 * 1.01 g/mol + 16.00 g/mol = 30.03 g/mol. To find the molecular formula, we divide the molar mass of the compound by the molar mass of the empirical formula and multiply each element in the empirical formula by this number:

132.1 g/mol / 30.03 g/mol = 4.40

C = 1 * 4.40 = 4.40

H = 2 * 4.40 = 8.80

O = 1 * 4.40 = 4.40

The molecular formula of the compound is therefore C4H8O4.

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