Final answer:
The empirical formula of a compound composed of 25.3 g of potassium and 5.18 g of oxygen is K2O. This is determined by converting the masses to moles, then finding the simplest whole number ratio, which in this case is 2:1 for K:O.
Step-by-step explanation:
To determine the empirical formula of a compound composed of potassium (K) and oxygen (O), we need to convert the given masses to moles. The molar mass of potassium is 39.10 g/mol and the molar mass of oxygen is 16.00 g/mol. We then use these values to calculate the number of moles:
Moles of K = 25.3 g / 39.10 g/mol ≈ 0.647 moles
Moles of O = 5.18 g / 16.00 g/mol ≈ 0.324 moles. The next step is to divide each by the smallest number of moles to get the ratio of the elements:
Ratio of K:O = 0.647:0.324 ≈ 2:1.
Therefore, the empirical formula of the compound is K2O, which corresponds to option (a) K2O.