Serotonin is a compound that conducts nerve impulses in the brain. It contains 68.2% C, 6.86% H, 15.9% N, and 9.08% O. Its molar mass is 176 g/mol Determine its molecular formula.

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Step 1: Assume you have 100 g of serotonin, which allows you to directly convert the percentage composition to grams. This means you have 68.2 g of C, 6.86 g of H, 15.9 g of N, and 9.08 g of O.

Step 2: Convert the mass of each element to moles by dividing by their respective atomic masses: C (12.01 g/mol), H (1.008 g/mol), N (14.01 g/mol), and O (16.00 g/mol).

Step 3: Determine the simplest whole number ratio of moles of each element by dividing each by the smallest number of moles calculated in Step 2.

Step 4: Use the simplest whole number ratio to write the empirical formula of serotonin.

Step 5: Calculate the empirical formula mass and divide the given molar mass (176 g/mol) by the empirical formula mass to find the ratio needed to convert the empirical formula to the molecular formula. Multiply the subscripts in the empirical formula by this ratio to get the molecular formula.

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Key Concepts

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

Empirical Formula

The empirical formula represents the simplest whole-number ratio of the elements in a compound. To determine the empirical formula, the percentage composition of each element is converted to moles, and then the ratios of these moles are simplified to the smallest whole numbers. This provides a foundational understanding of the compound's composition before deriving the molecular formula.

Molecular Formula

The molecular formula indicates the actual number of atoms of each element in a molecule of a compound. It can be derived from the empirical formula by multiplying the subscripts by a whole number, which is determined by the ratio of the compound's molar mass to the empirical formula mass. This formula provides more specific information about the compound's structure and composition.

Molar Mass Calculation

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all the atoms in the molecular formula. Understanding how to calculate molar mass is essential for converting between grams and moles, which is crucial for determining the molecular formula from the empirical formula and the given molar mass.

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