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Ch.3 - Chemical Reactions and Reaction Stoichiometry
Chapter 3, Problem 24e

Determine the formula weights of each of the following compounds: e. benzaldehyde, C6H5CHO, the molecule largely responsible for the odor of almond extract.

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Step 1: Identify the number of each type of atom in the compound. For benzaldehyde, C6H5CHO, there are 7 carbon atoms (C), 6 hydrogen atoms (H), and 1 oxygen atom (O).
Step 2: Look up the atomic weights of each type of atom on the periodic table. The atomic weights are approximately 12.01 g/mol for carbon, 1.01 g/mol for hydrogen, and 16.00 g/mol for oxygen.
Step 3: Multiply the atomic weight of each type of atom by the number of atoms of that type in the compound. For example, for carbon in benzaldehyde, you would multiply 12.01 g/mol by 7.
Step 4: Add up the results from step 3 for all types of atoms in the compound. This will give you the formula weight of the compound.
Step 5: Remember that the formula weight is usually reported in units of grams per mole (g/mol).

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Key Concepts

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

Molecular Formula

A molecular formula represents the number and types of atoms in a molecule. For benzaldehyde, C6H5CHO, the formula indicates it contains 6 carbon (C) atoms, 5 hydrogen (H) atoms, and 1 oxygen (O) atom. Understanding the molecular formula is essential for calculating the compound's formula weight.
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Formula Weight

Formula weight, also known as molecular weight, is the sum of the atomic weights of all atoms in a molecular formula. It is typically expressed in atomic mass units (amu). To find the formula weight of benzaldehyde, one must multiply the number of each type of atom by its respective atomic weight and sum these values.
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Atomic Weights

Atomic weights are the average masses of an element's isotopes, measured in atomic mass units (amu). For example, the atomic weights of carbon, hydrogen, and oxygen are approximately 12.01, 1.008, and 16.00 amu, respectively. Accurate knowledge of these weights is crucial for calculating the formula weight of compounds like benzaldehyde.
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