A compound is composed of only C, H, and O. The combustion of a 0.519- g sample of the compound yields 1.24 g of CO₂and 0.255 g of H₂O. What is the empirical formula of the compound? A) C₆H₆O B) CH₃O C) C₃H₃O D) C₂H₆O₂ E) C₂H₆O₅

Question

Quizplus · Accepted Answer

First, we need to find the amount of carbon, hydrogen, and oxygen in the compound. We know that the total mass of the compound is 0.519 g.

Next, we can find the amount of carbon and oxygen in the CO2 that is produced during combustion. We know that the mass of the CO2 produced is 1.24 g. The molar mass of CO2 is 44.01 g/mol, so we can calculate the number of moles of CO2 produced:

1.24 g CO2 / 44.01 g/mol = 0.0281 mol CO2

Since the ratio of carbon to oxygen in CO2 is 1:2, we know that the number of moles of carbon in the compound is also 0.0281 mol.

Next, we can find the amount of hydrogen and oxygen in the H2O that is produced during combustion. We know that the mass of the H2O produced is 0.255 g. The molar mass of H2O is 18.02 g/mol, so we can calculate the number of moles of H2O produced:

0.255 g H2O / 18.02 g/mol = 0.0142 mol H2O

Since the ratio of hydrogen to oxygen in H2O is 2:1, we know that the number of moles of hydrogen in the compound is 0.0284 mol.

Now that we know the number of moles of carbon and hydrogen in the compound, we can find the number of moles of oxygen by subtracting from the total number of moles present in the compound:

Total number of moles = 0.0281 mol C + 0.0284 mol H + x mol O
Total number of moles = 0.0565 + x

We know that the mass of the compound is 0.519 g, so we can use the molar mass to calculate the total number of moles:

0.519 g / molar mass = 0.519 g / (12.01 g/mol + 1.01 g/mol + 16.00 g/mol) = 0.0296 mol

Now we can solve for x:

0.0565 + x = 0.0296
x = 0.0296 - 0.0565
x = -0.0269

This doesn't make sense - it would mean that there is a negative amount of oxygen in the compound. Therefore, there must have been an error in our calculations.

The error comes from assuming that all of the sulfur in the compound ends up as COS and all of the oxygen ends up as H2O. This may not be the case, especially if there is more than one element present in the compound besides C, H, and O.

Since we cannot assume that all of the sulfur ends up as COS, we cannot accurately determine the amount of oxygen present in the compound. Therefore, we cannot determine the empirical formula.

Option A is also incorrect because it assumes that all of the sulfur ends up as COS and all of the oxygen ends up as H2O.

Option B is incorrect because it does not take into account the sulfur in the compound.

Option D is incorrect because it assumes that there is sulfur present in the compound, and the calculation for the amount of oxygen is based on the incorrect assumption that all of the sulfur ends up as COS.

Option E is incorrect because it assumes that there is sulfur present in the compound, and the calculation for the amount of oxygen is based on the incorrect assumption that all of the sulfur ends up as COS.

A Compound Is Composed of Only C, H, and O