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Ch.2 - Atoms, Molecules & Ions
Chapter 2, Problem 141

Lactic acid, a compound found both in sour milk and in tired muscles, has the structure shown. What is its chemical formula?

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Identify the elements present in the lactic acid structure: carbon (C), hydrogen (H), and oxygen (O).
Count the number of each type of atom in the structure. Typically, lactic acid has 3 carbon atoms, 6 hydrogen atoms, and 3 oxygen atoms.
Write the chemical formula by listing each element followed by the number of atoms of that element in subscript. For example, if there are 3 carbon atoms, it would be written as C_3.
Combine the counts of each element into a single chemical formula, ensuring the order is typically C, H, then O.
Double-check the structure to ensure all atoms are accounted for and the formula accurately represents the structure.

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Key Concepts

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

Chemical Structure

The chemical structure of a compound refers to the arrangement of atoms within the molecule, including the types of atoms and the bonds between them. Understanding the structure of lactic acid, which includes a hydroxyl group (-OH) and a carboxylic acid group (-COOH), is essential for determining its chemical formula.
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Molecular Formula

A molecular formula represents the number and types of atoms in a molecule. For lactic acid, the molecular formula is derived from its structure, indicating the specific counts of carbon (C), hydrogen (H), and oxygen (O) atoms present in the compound, which is crucial for identifying it correctly.
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Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. Lactic acid contains both a hydroxyl group and a carboxylic acid group, which influence its properties and reactivity, and are key to understanding its behavior in biological systems.
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