Xanthotoxin is a natural product extracted from the fruits...

Xanthotoxin is a natural product extracted from the fruits of Heracleum persicum that seems to have some success in treating a skin discase known as psoriasis. a. Combustion of $0.0100 \mathrm{g}$ of xanthotoxin in excess oxygen yielded $0.0244 \mathrm{g} \mathrm{CO}_{2}$ and $0.00333 \mathrm{g} \mathrm{H}_{2} \mathrm{O}$ Calculate the empirical formula of xanthotoxin. b. A solution of $0.250 \mathrm{g}$ xanthotoxin in $10.0 \mathrm{g}$ carbon tetrachloride causes the freezing point of the solution to decrease by $3.46^{\circ} \mathrm{C} .$ Given that $K_{f}$ for $\mathrm{CCl}_{4}$ is $29.8^{\circ} \mathrm{C} / \mathrm{m}$ and that xanthotoxin is a nonelectrolyte, calculate the molar mass and molecular formula of xanthotoxin.

Xanthotoxin is a natural product extracted from the fruits of Heracleum persicum that seems to have some success in treating a skin discase known as psoriasis.
a. Combustion of $0.0100 \mathrm{g}$ of xanthotoxin in excess oxygen yielded $0.0244 \mathrm{g} \mathrm{CO}_{2}$ and $0.00333 \mathrm{g} \mathrm{H}_{2} \mathrm{O}$
Calculate the empirical formula of xanthotoxin.
b. A solution of $0.250 \mathrm{g}$ xanthotoxin in $10.0 \mathrm{g}$ carbon tetrachloride causes the freezing point of the solution to decrease by $3.46^{\circ} \mathrm{C} .$ Given that $K_{f}$ for $\mathrm{CCl}_{4}$ is $29.8^{\circ} \mathrm{C} / \mathrm{m}$ and that xanthotoxin is a nonelectrolyte, calculate the molar mass and molecular formula of xanthotoxin.

Key Concepts

Molecular Formula Construction

The molecular formula provides the actual number of atoms of each element in a molecule and is determined by comparing the empirical formula mass with the experimentally determined molar mass. The appropriate multiple, which relates these two, is then applied to the empirical formula to yield the molecular formula.

Molar Mass Determination

Molar mass determination using colligative properties involves correlating the observed change in a physical property (such as freezing point depression) with the concentration of dissolved solute. This allows for the calculation of the number of moles present in a known mass of solute, which is essential for determining the molar mass and, in conjunction with the empirical formula, the molecular formula.

Freezing Point Depression

Freezing point depression is a colligative property that quantifies how much the freezing point of a solvent is lowered when a solute is dissolved in it. Using the measured freezing point change and the known cryoscopic constant of the solvent, one can calculate the molality of the solution and ultimately deduce the molar mass of the solute.

Colligative Properties

Colligative properties are physical properties of a solution that depend on the number of solute particles rather than their specific nature. They include phenomena like freezing point depression and boiling point elevation, and are useful in determining the molar mass of solute molecules.

Empirical Formula Determination

The empirical formula represents the simplest whole-number ratio of the elements in a compound. Data obtained from combustion analysis can be converted from mass to moles for each element, which are then compared to establish the final empirical formula.

Combustion Analysis

Combustion analysis is a technique used to determine the elemental composition of an organic compound by burning it in oxygen and measuring the masses of the resulting combustion products, typically CO2 and H2O. This data allows for the calculation of the amounts of carbon and hydrogen present in the original sample.

Transcript

Please give Ace some feedback