A compound is found to have 56.4% potassium, 8.7% carbon, and 34.9% oxygen. What is the empirical formula?
k2co3
To determine the empirical formula of a compound, we need to determine the ratio of the different elements present in the compound. The percentage composition of each element can be used to find this ratio.
Step 1: Convert percentages to grams.
Let's assume we have a 100g sample of the compound. This means that we have 56.4g of potassium, 8.7g of carbon, and 34.9g of oxygen.
Step 2: Convert grams to moles.
To convert grams to moles, we need to divide the mass of each element by its molar mass. The molar mass is the atomic mass of an element found on the periodic table.
- The atomic mass of potassium (K) is 39.1 g/mol.
- The atomic mass of carbon (C) is 12.0 g/mol.
- The atomic mass of oxygen (O) is 16.0 g/mol.
Now, we can determine the number of moles for each element:
- Moles of potassium (K): 56.4 g / 39.1 g/mol ≈ 1.44 mol
- Moles of carbon (C): 8.7 g / 12.0 g/mol ≈ 0.725 mol
- Moles of oxygen (O): 34.9 g / 16.0 g/mol ≈ 2.18 mol
Step 3: Divide by the smallest number of moles.
To obtain the simplest whole-number ratio, we need to divide the number of moles of each element by the smallest number of moles. In this case, carbon (C) has the smallest number of moles (0.725 mol).
- Moles of potassium (K): 1.44 mol / 0.725 mol ≈ 1.99 (round to 2)
- Moles of carbon (C): 0.725 mol / 0.725 mol = 1
- Moles of oxygen (O): 2.18 mol / 0.725 mol ≈ 3
Step 4: Write the empirical formula using the ratios.
Now that we have the mole ratio, we can write the empirical formula using the respective symbols for each element.
The empirical formula is K2C3O6.