Final answer:
To determine the empirical formula, the moles of carbon, hydrogen, and oxygen are calculated from the masses of CO₂ and H₂O produced by combustion. The empirical formula represents the simplest whole number ratio of the elements, which in this case is CH₃O.
Step-by-step explanation:
Determining the Empirical Formula
The student is given a compound containing only carbon, hydrogen, and oxygen. Upon combustion, 4.197 g of CO₂ are produced, which corresponds to the carbon in the original compound, and 2.578 g of H₂O, which corresponds to the hydrogen in the compound. The initial mass of the compound was 2.197 g.
To find the empirical formula, we must first calculate the moles of carbon and hydrogen using the masses of CO₂ and H₂O produced:
- C in CO₂: (4.197 g CO₂) × (1 mol CO₂ / 44.01 g CO₂) × (1 mol C / 1 mol CO₂) = 0.0954 mol C
- H in H₂O: (2.578 g H₂O) × (1 mol H₂O / 18.02 g H₂O) × (2 mol H / 1 mol H₂O) = 0.2856 mol H
Next, we determine the mass of oxygen in the compound by subtracting the masses of carbon and hydrogen from the initial mass:
Mass of O: 2.197 g (initial mass) - (0.0954 mol C × 12.01 g/mol C) - (0.2856 mol H × 1.008 g/mol H) = 1.5131 g O
Now, we calculate the moles of oxygen:
Moles of O: (1.5131 g O) × (1 mol O / 16.00 g/mol O) = 0.0946 mol O
To get the empirical formula, we divide the mole amounts by the smallest number of moles:
Ratio of C:H:O = 0.0954 mol C : 0.2856 mol H : 0.0946 mol O. After dividing through by the smallest number of moles (which in this case is 0.0946 mol O), we get a ratio close to 1:3:1.
The empirical formula that reflects this ratio is CH₃O (Answer a)