Question

Skunks Analysis of skunk spray yields a molecule with 44.77% C, 7.46% H and 47.76% S. What is the chemical formula for this molecule found in the spray from skunks that scientists think is partly responsible for the strong odor?

Short answer

The empirical chemical formula for the molecule found in skunk spray that is partly responsible for its strong odor is \(C_2H_5S\).

Step-by-step solution

Calculate the moles of elements in a 100g sample

We will first assume that we have a 100g sample of the molecule. With this assumption, we can use the given percentage of each element to find the mass of each element: Carbon (C): 44.77% of 100g Hydrogen (H): 7.46% of 100g Sulfur (S): 47.76% of 100g Now we can convert these masses into moles using the molar mass of each element: Carbon (C): 12.01 g/mol Hydrogen (H): 1.01 g/mol Sulfur (S): 32.06 g/mol

Find the mole to mole ratio of each element

To find the ratio of elements in the molecule, we need to divide the moles of each element by the smallest number of moles: Moles of C = (44.77g) / (12.01g/mol) = 3.73 mol Moles of H = (7.46g) / (1.01g/mol) = 7.39 mol Moles of S = (47.76g) / (32.06g/mol) = 1.49 mol Divide each number by the smallest mole value (1.49 mol): Ratio = (Moles of C: 3.73/1.49 , Moles of H: 7.39/1.49 , Moles of S: 1.49/1.49) Ratio ≈ (2.5 , 4.96 , 1)

Determine the smallest whole number ratio of each element

In this case, we can round the decimal values to the nearest whole numbers to find the empirical formula of the molecule found in skunk spray. These are the closest whole numbers to the previously calculated ratio. Empirical formula: C_2H_5S

Present the final empirical chemical formula

The empirical chemical formula for the molecule found in skunk spray that is partly responsible for its strong odor is C_2H_5S.

Key concepts

Chemical Composition

When investigating the substance responsible for the notorious skunk odor, scientists are essentially deciphering its chemical composition. Chemical composition refers to the elements a substance is comprised of, along with their respective proportions.

In the case of skunk spray, the composition is detailed through percentages of carbon (C), hydrogen (H), and sulfur (S). Understanding this composition is vital as it's the first step towards determining the empirical formula; a formula that reflects the simplest whole-number ratio of the atoms in the compound.

An empirical formula doesn't necessarily represent the exact number of atoms in a molecule (that's the molecule's molecular formula), but it provides crucial information about the proportional relationship of elements within a molecule. This fundamental stepping stone in chemistry is a concise way to represent a compound's composition without detailing the structure or the actual number of atoms involved in a complex molecule's architecture.

Molar Mass

Molar mass is essentially the weight of one mole (approximately 6.022 x 10^23 particles) of a substance, usually expressed in grams per mole (g/mol). It is unique to each element, as it's determined by the weighted average of the isotopic masses of the element's naturally occurring isotopes.

For instance, the elements in the skunk spray were converted to moles using their respective molar masses: carbon with a molar mass of 12.01 g/mol, hydrogen with 1.01 g/mol, and sulfur with 32.06 g/mol. These values are derived from the periodic table, which lists the atomic weight (virtually the same as molar mass) for each element. Molar mass plays a pivotal role in the conversion from mass to moles, allowing us to translate the percentage composition by mass to a molar proportion, which is used in finding the empirical formula.

Mole-to-Mole Ratio

In order to reveal the simplest ratio of the elements within a compound, scientists utilize the mole-to-mole ratio. It's key in deriving an empirical formula and involves comparing the moles of each element present.

The procedure includes dividing the moles of each component by the smallest number of moles amongst the elements in the sample. By doing so, we can determine the simplest whole-number ratio that describes the relative number of atoms of each kind in the chemical substance.

Following the analysis of the skunk spray, when the numbers of moles for carbon, hydrogen, and sulfur were determined—3.73 mol for carbon, 7.39 mol for hydrogen, and 1.49 mol for sulfur—they were then each divided by the smallest value (1.49 mol for sulfur). This calculation simplifies the ratio, leading to an approximate mole-to-mole ratio which is crucial for determining the empirical formula (C₂H₅S in this case), thereby providing a foundational aspect of the substance's chemical identity.