Finding Empirical Formula of Propenoic Acid

In summary, the conversation discusses the use of propenoic acid in industries and determining its empirical formula through a combustion experiment. After calculating the masses of carbon, hydrogen, and oxygen, the empirical formula is found to be C3H4O2.
  • #1
Drakkith
Mentor
22,988
7,367

Homework Statement


[/B]
Propenoic acid is a reactive organic liquid used in the manufacture of plastics, coatings, and adhesives. An unlabeled container is thought to contain this acid. A 0.2033-g sample is combusted in an apparatus such as that shown below. The gain in mass of the H2O absorber is 0.102 g, whereas that of the CO2 absorber is 0.374 g.
(Mass gained by each absorber corresponds to the mass of CO2 or H2O produced)

What is the empirical formula of propenoic acid?

Homework Equations



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The Attempt at a Solution


First and foremost, I don't even know what propenoic acid consists of at all, other than carbon and hydrogen (since neither comes from the air). I'm going under the assumption that it has oxygen as well. It has to consist of something else other than C and H, as there's 0.08983 grams of our sample left over. Since nothing else other than C, H, and O is produced as a product, it narrows it down to O.

Finding the mass of C and H:

Carbon's mass per mol is 12.01 g, so it makes up 27.289% of the mass of CO2. So 0.374 g CO2 contains 0.10206 g C.

Hydrogen's mass per mol is 2.016, so it makes up 11.19% of the mass of H2O, giving us a mass of 0.01141 g H.

.2033 g of Sample - 0.10206 g C- 0.01141 g H= 0.08983 g O.

Mole ratio:

0.10206g C / 12.01 g/mol C = 0.0084979 mol C.

0.01141 g H / 2.016 g/mol H = 0.0056597 mol H.

0.08983 g O / 16 g/mol O = 0.0056144 mol O.

Dividing the mols of C, H, and O by number of moles of O gives me 1.5, 1, and 1 as subscripts. Multiply by 2 to get a whole number ratio and I get C3H2O2. But this is incorrect according to the mastering chemistry website we use for our homework. I'm not sure what I've done wrong.
 
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  • #2
Drakkith said:
0.01141 g H / 2.016 g/mol H = 0.0056597 mol H.

You have the wrong atomic mass of hydrogen.
 
  • #3
Ygggdrasil said:
You have the wrong atomic mass of hydrogen.

Sigh... I used the mass of H2...

Okay. Using the correct atomic mass gives me C3H4O2, which turns out to be correct. Thanks!
 

Related to Finding Empirical Formula of Propenoic Acid

1. What is the empirical formula of propenoic acid?

The empirical formula of propenoic acid is C3H4O2.

2. How is the empirical formula of propenoic acid determined?

The empirical formula of propenoic acid is determined through experimental data, specifically the mass and composition of the compound.

3. What is the difference between empirical and molecular formula?

The empirical formula is the simplest whole number ratio of atoms in a compound, while the molecular formula shows the actual number of atoms in a molecule.

4. Can the empirical formula of propenoic acid be changed?

No, the empirical formula of a compound cannot be changed as it is based on the actual ratio of atoms in the compound.

5. How does the empirical formula of propenoic acid relate to its chemical properties?

The empirical formula can provide information about the chemical properties of propenoic acid, such as its molecular weight and the number of carbon, hydrogen, and oxygen atoms present. This information can be used to predict the compound's behavior in chemical reactions and its physical properties.

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