Ma huang, an extract from the ephedra species of plants,...

Ma huang, an extract from the ephedra species of plants, contains ephedrine. The Chinese have used this herb for more than 5000 years to treat asthma. More recently, ephedrine has been used in diet pills that can be purchased over the counter in herbal medicine shops. However, very serious concerns have been raised regarding these pills following reports that their use led to serious heart problems. (a) A molecular model of ephedrine is drawn below. From this determine the molecular formula for ephedrine and calculate its molar mass. (b) What is the weight percent of carbon in ephedrine? (c) Calculate the amount (moles) of ephedrine in a 0.125 g sample. (d) How many molecules of ephedrine are there in $0.125 \mathrm{g} ?$ How many $\mathrm{C}$ atoms?

Ma huang, an extract from the ephedra species of plants, contains ephedrine. The Chinese have used this herb for more than 5000 years to treat asthma. More recently, ephedrine has been used in diet pills that can be purchased over the counter in herbal medicine shops. However, very serious concerns have been raised regarding these pills following reports that their use led to serious heart problems.
(a) A molecular model of ephedrine is drawn below. From this determine the molecular formula for ephedrine and calculate its molar mass.
(b) What is the weight percent of carbon in ephedrine?
(c) Calculate the amount (moles) of ephedrine in a 0.125 g sample.
(d) How many molecules of ephedrine are there in $0.125 \mathrm{g} ?$ How many $\mathrm{C}$ atoms?

Key Concepts

Mole Concept

The mole is a fundamental unit in chemistry that allows chemists to count particles by relating mass to a specific number of entities, namely Avogadro's number. This concept enables the conversion between mass, number of moles, and the number of molecules, forming the basis of quantitative chemical analysis and stoichiometry.

Percent Composition

Percent composition, or weight percent, is the calculation of the percentage by mass of each element in a compound relative to the total molecular mass. This concept is vital for understanding the relative contribution of different elements to the overall mass of a compound and is commonly used in both analytical chemistry and material science.

Avogadro’s Number

Avogadro’s number (approximately 6.022 × 10^23) is the number of atoms, ions, or molecules in one mole of a substance. It provides the bridge between the macroscopic scale of substances we handle in the laboratory and the microscopic scale of individual atoms and molecules, and is crucial for calculations involving the number of particles in a given sample.

Molecular Formula Determination

This concept involves identifying how many atoms of each element are present in a molecule based on its structural formula. In the broader context of chemistry, it is fundamental to understanding a compound’s composition and is the first step in any quantitative analysis of a substance.

Molar Mass Calculation

Molar mass is the mass of one mole of a substance, usually expressed in grams per mole. Calculating the molar mass requires summing the atomic masses of all the atoms present in the molecular formula, a key step in connecting the macroscopic mass of a substance with the microscopic count of its molecules.

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