Percent Composition and Empirical Formulas

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Percent Composition Noun

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[per-sent kom-puh-zish-un]

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Percent Composition

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The percentage by mass of each element present in a compound, which expresses the relative amounts of the elements.

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Example: This image shows the formula for percent composition, which calculates an element's mass percentage in a compound by dividing its mass by the total compound mass.

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Law of Definite Proportions Noun

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[law uv def-uh-nit pruh-por-shuns]

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Law of Definite Proportions

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A chemical law stating that a given compound always contains its component elements in a fixed ratio by mass.

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Example: This image shows a model of a carbon dioxide (CO₂) molecule, which always contains one carbon atom and two oxygen atoms in a fixed ratio.

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Law of Constant Composition Noun

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[law uv kon-stunt kom-puh-zish-un]

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Law of Constant Composition

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A chemical law stating that any sample of a pure compound will consist of the same elements in the same mass ratio.

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Example: A glucose molecule always has 6 carbon, 12 hydrogen, and 6 oxygen atoms, showing that a compound has a fixed ratio of elements.

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N-P-K Ratio Noun

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[en-pee-kay rey-shee-oh]

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N-P-K Ratio

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A ratio representing the percent composition of the essential plant nutrients nitrogen (N), phosphorus (P), and potassium (K) in fertilizer.

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Example: This diagram shows a fertilizer bag with the numbers 2-0-24, explaining that these represent the percent composition of Nitrogen (2%), Phosphorus (0%), and Potassium (24%).

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Molar Mass Noun

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[moh-ler mas]

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Molar Mass

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The mass of one mole of a substance, which is typically expressed in units of grams per mole (g/mol).

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Example: This image shows how to find the molar mass of a compound (CO2) by adding the atomic masses of its individual atoms (one Carbon and two Oxygen).

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Deuterium Noun

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[doo-teer-ee-um]

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Deuterium

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A stable isotope of hydrogen containing one proton and one neutron, making its mass about twice that of ordinary hydrogen.

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Example: This diagram shows Deuterium is an isotope of Hydrogen. It has one proton and one electron, like Hydrogen, but also includes one neutron, which Hydrogen lacks.

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Empirical Formula Noun

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[em-pir-i-kuhl for-myoo-luh]

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Empirical Formula

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A chemical formula showing the simplest whole-number ratio of atoms or moles of the elements in a particular compound.

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Example: This table shows how an empirical formula is the simplest whole-number ratio of atoms in a compound, like how glucose's C6H12O6 simplifies to CH2O.

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Molecular Formula Noun

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[muh-lek-yuh-ler for-myoo-luh]

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Molecular Formula

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A chemical formula that indicates the actual number of atoms of each element present in one molecule of a compound.

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Example: This image shows a model of a water molecule, linking its visual structure (two H atoms, one O atom) directly to its written molecular formula, H₂O.

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Empirical Formula Mass Noun

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[em-pir-i-kuhl for-myoo-luh mas]

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Empirical Formula Mass

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The sum of the atomic masses of all atoms in a compound's empirical formula, expressed in grams per mole.

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Example: This table shows the empirical formula mass, which is the mass of the simplest whole-number ratio of atoms (the empirical formula), like ~17 g/mol for HO.

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Monosaccharide Noun

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[mon-oh-sak-uh-rahyd]

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Monosaccharide

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The simplest form of a carbohydrate, also known as a simple sugar, which serves as a basic unit for complex carbohydrates.

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Example: This diagram shows the chemical structure of a monosaccharide, allowing you to count the individual carbon (C), hydrogen (H), and oxygen (O) atoms.