A compound is found to have 56.4% potassium, 8.7% carbon, and 34.9% oxygen. What is the empirical formula?
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To determine the empirical formula of a compound, you need to calculate the simplest, whole number ratio of the elements present in the compound. We can follow these steps:
Step 1: Convert the percentage of each element to grams.
- Potassium: 56.4% of the compound, which means 56.4 grams.
- Carbon: 8.7% of the compound, which means 8.7 grams.
- Oxygen: 34.9% of the compound, which means 34.9 grams.
Step 2: Convert the mass of each element to moles.
- To do this, divide the grams of each element by its molar mass.
- For potassium, the molar mass is 39.10 g/mol.
- For carbon, the molar mass is 12.01 g/mol.
- For oxygen, the molar mass is 16.00 g/mol.
- Moles of potassium (K) = 56.4 g / 39.10 g/mol = 1.44 mol
- Moles of carbon (C) = 8.7 g / 12.01 g/mol = 0.724 mol
- Moles of oxygen (O) = 34.9 g / 16.00 g/mol = 2.18 mol
Step 3: Divide each mole value by the smallest mole value to obtain a whole number ratio.
- In this case, the smallest mole value is 0.724 mol (corresponding to carbon).
- Dividing the moles of each element by 0.724 gives us:
- Moles of potassium (K) = 1.44 mol / 0.724 mol ≈ 1.99 ≈ 2
- Moles of carbon (C) = 0.724 mol / 0.724 mol = 1
- Moles of oxygen (O) = 2.18 mol / 0.724 mol ≈ 3.01 ≈ 3
Step 4: Write the empirical formula using the whole number ratio obtained.
- The empirical formula for the compound is K2C3O3.
Therefore, the empirical formula of the compound is K2C3O3.