a. A compound is determined to have a molar mass of \(58.12 \mathrm{~g} / \mathrm{mol}\) and an empirical formula of \(\mathrm{C}_{2} \mathrm{H}_{5}\); determine the molecular formula for this compound. b. Benzene is an intermediate in the production of many important chemicals used in the manufacture of plastics, drugs, dyes, detergents and insecticides. Benzene has an empirical formula of CH. It has a molar mass of \(78.11 \mathrm{~g} / \mathrm{mol}\). What is the molecular formula?

The empirical formula of a chemical compound is a simple expression of the relative number of each type of atom in the compound. Imagine it as the building block of a compound's identity. It provides the simplest whole number ratio of the elements in the molecule, but does not necessarily represent the actual numbers of atoms found in the molecule. For example, glucose has an empirical formula of CH2O, indicating a 1:2:1 ratio of carbon, hydrogen, and oxygen atoms, respectively.

To determine the empirical formula, one often starts with the mass percentages of each element, which could be obtained from experimental data. By converting these percentages to moles, and then finding the simplest mole ratio of the elements, the empirical formula can be established. In our exercise example, the empirical formula of the compound is given as C2H5. This tells us that for every 2 moles of carbon, there are 5 moles of hydrogen in the simplest ratio.

The molar mass of a substance is the weight of one mole (approximately 6.022 x 10^23 particles) of that substance and is expressed in grams per mole (g/mol). It can be thought of as the collective weight of all the atoms in a given formula and is calculated by summing the atomic masses of all the elements in the compound, multiplied by their respective number of atoms (their subscript in the chemical formula).

For example, to calculate the molar mass of a compound with the empirical formula C2H5, add the mass of two carbon atoms (2 x 12.01 g/mol) to the mass of five hydrogen atoms (5 x 1.008 g/mol). Having the molar mass allows us to relate mass in grams to amount in moles, which is a fundamental step in stoichiometry. Knowing the empirical formula and the molar mass, we can find out the true molecular formula of substances, as we do for benzene in the exercise.

Analyzing a chemical compound involves determining its composition and structure, which includes identifying its empirical formula and molar mass. This can be done through experiments such as combustion analysis or mass spectrometry. Once the percentages of each element within a compound are known, these values can be used to deduce the empirical formula as previously discussed.

Understanding the Composition

Insights into a compound's properties and potential reactions can be gained from knowing its composition. The given exercises are examples of how chemical compound analysis can determine the quantities and ratios of elements, revealing important details about the molecular structure.

Following the determination of the empirical formula and molar mass, we gain an understanding of the substance's properties. For instance, in pharmaceuticals, the precise arrangement of atoms can dictate the effectiveness of a drug, which underscores the importance of accurate chemical analysis.

Stoichiometry refers to the quantitative relationships between the amounts of reactants and products in a chemical reaction. It is based on the conservation of mass and the concept of the mole. Stoichiometry can predict how much product will form during a reaction, or how much reactant is needed to produce a desired amount of product.

To perform stoichiometric calculations, one must balance chemical equations, convert mass to moles (and vice versa), and use molar ratios from the balanced equation as conversion factors.

Real-World Applications

It's crucial in fields such as engineering and pharmacology, where precise amounts of substances must be used. By employing the stoichiometry in our exercise, the students can predict how many moles of a reactant are required to form a product, allowing the determination of the molecular formula from the empirical formula and the molar mass.