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What are the empirical formulas of the compounds with the following compositions? (a) 2.1 percent h, 65.3 percent 0, 32.6 percent s; (b) 20.2 percent Al, 79.8 percent Cl. What are the empirical formulas of the compounds with the following compositions? (a) 40.1 percent c, 6.6 percent h, 53.3 percent o; (b) 18.4 percent c, 21.5 percent n, 60.1 percent k ?hydrogen is 1.008 solve it accurately
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Here's how to determine the empirical formulas:
Determining Empirical Formulas
1. Assume a 100 g Sample: This makes the percentages directly translate to grams.
2. Convert Grams to Moles: Divide the mass of each element by its molar mass (found on the periodic table).
3. Find the Simplest Mole Ratio: Divide each of the mole values by the smallest mole value. This will give you the ratio of elements in the empirical formula.
4. Round to Whole Numbers (if necessary): If the ratios are not already close to whole numbers, multiply them by a common factor to obtain whole numbers.
Example (a) 2.1% H, 65.3% O, 32.6% S
Step 1: 2.1 g H, 65.3 g O, 32.6 g S
Step 2:
H: 2.1 g / 1.008 g/mol = 2.08 mol
O: 65.3 g / 16.00 g/mol = 4.08 mol
S: 32.6 g / 32.06 g/mol = 1.02 mol
Step 3:
H: 2.08 mol / 1.02 mol = 2.04
O: 4.08 mol / 1.02 mol = 4.00
S: 1.02 mol / 1.02 mol = 1.00
Step 4: The ratio is approximately 2:4:1. The empirical formula is H₂O₄S (simplified to H₂SO₄)
Repeat the same steps for the other examples.
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