Determine the empirical formulas of the compounds with the following compositions by mass: (a) 42.1% Na, 18.9% P, and 39.0% O (b) 18.7% Li, 16.3% C, and 65.0% O

검증된 단계별 안내

Convert the percentages into masses assuming you have 100 grams of the compound. This means you have 42.1 grams of Na, 18.9 grams of P, and 39.0 grams of O.

Calculate the number of moles of each element in the compound using their atomic masses (Na = 22.99 g/mol, P = 30.97 g/mol, O = 16.00 g/mol). Number of moles = mass of element (g) / atomic mass of element (g/mol).

Divide the number of moles of each element by the smallest number of moles calculated in the previous step to get a simple mole ratio of the elements.

If the mole ratios are not whole numbers, multiply all ratios by the smallest number that converts all ratios to whole numbers. This is often necessary to get the simplest whole number ratio of atoms in the empirical formula.

Write the empirical formula using the elements symbol followed by the whole number mole ratios as subscripts.

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주요 개념

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Empirical Formula

The empirical formula of a compound represents the simplest whole-number ratio of the elements present in that compound. It is derived from the mass percentages of each element, which are converted to moles and then simplified to the smallest integer ratio. This formula provides essential information about the composition of the compound without indicating the actual number of atoms in a molecule.

Mole Concept

The mole is a fundamental unit in chemistry that quantifies the amount of substance. One mole corresponds to Avogadro's number, approximately 6.022 x 10²³ entities (atoms, molecules, etc.). To determine the empirical formula, the mass percentages of elements are converted to moles by dividing by their respective atomic masses, allowing for the calculation of the simplest ratio of the elements.

Mass Percent Composition

Mass percent composition refers to the percentage by mass of each element in a compound. It is calculated by dividing the mass of each element in a sample by the total mass of the compound and multiplying by 100. This information is crucial for determining the empirical formula, as it provides the necessary data to convert to moles and establish the ratio of elements.