What are the empirical formulas of substances with the following mass percent compositions? (c) Sodium thiosulfate (photographic 'fixer'): 30.36% O, 29.08% Na, 40.56% S

Verified step by step guidance

1. Step 1: Assume a 100 g sample of the compound, which allows you to directly convert the percentage of each element to grams.
2. Step 2: Convert the mass of each element to moles by dividing by their respective molar masses: Na (22.99 g/mol), S (32.07 g/mol), and O (16.00 g/mol).
3. Step 3: Determine the mole ratio of the elements by dividing each element's mole value by the smallest number of moles calculated in Step 2.
4. Step 4: If necessary, multiply the ratios by a whole number to obtain whole numbers for each element in the empirical formula.
5. Step 5: Write the empirical formula using the whole number ratios as subscripts for each element.

Key Concepts

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 percent composition of the elements, allowing chemists to determine the relative amounts of each element without knowing the actual molecular structure.

Mass Percent Composition

Mass percent composition indicates 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 sample and multiplying by 100. This information is crucial for converting mass percentages into moles, which is necessary for determining the empirical formula.

Mole Concept

The mole concept is a fundamental principle in chemistry that relates the mass of a substance to the number of particles (atoms, molecules, or ions) it contains. One mole of any substance contains Avogadro's number (approximately 6.022 x 10²³) of particles. This concept is essential for converting mass percent compositions into moles, which can then be used to find the empirical formula.