What are the molecular (formula) weights of the following substances? (b) C4H8O2 (butyric acid, responsible for the odor of rancid butter)

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Identify the molecular formula of the compound: C_4H_8O_2.

Determine the atomic weights of each element from the periodic table: Carbon (C) is approximately 12.01 g/mol, Hydrogen (H) is approximately 1.01 g/mol, and Oxygen (O) is approximately 16.00 g/mol.

Calculate the total weight contributed by each element: Multiply the atomic weight of Carbon by 4, Hydrogen by 8, and Oxygen by 2.

Add the total weights of all the elements together to find the molecular weight of C_4H_8O_2.

Ensure all units are consistent and the final molecular weight is expressed in g/mol.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molecular Weight

Molecular weight, also known as molar mass, is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is calculated by summing the atomic weights of all atoms in a molecular formula. For example, in butyric acid (C4H8O2), the molecular weight is determined by adding the weights of 4 carbon (C), 8 hydrogen (H), and 2 oxygen (O) atoms.

Atomic Weights

Atomic weights are the average masses of an element's isotopes, measured in atomic mass units (amu). These values are found on the periodic table and are essential for calculating molecular weights. For instance, the atomic weights for carbon, hydrogen, and oxygen are approximately 12.01 amu, 1.008 amu, and 16.00 amu, respectively, which are used to compute the molecular weight of compounds like butyric acid.

Empirical vs. Molecular Formula

The empirical formula represents the simplest whole-number ratio of elements in a compound, while the molecular formula shows the actual number of each type of atom in a molecule. Butyric acid has the molecular formula C4H8O2, indicating it contains 4 carbon, 8 hydrogen, and 2 oxygen atoms, which can also be derived from its empirical formula, C2H4O, showing the ratio of elements.

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Empirical vs Molecular Formula

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