Final answer:
After calculating the masses of each element in the chalcopyrite sample, converting these to moles, and finding the simplest whole number ratio of the elements, the empirical formula of chalcopyrite is determined to be CuFeS2.
Step-by-step explanation:
To calculate the empirical formula of chalcopyrite, we first need to find the amount of sulfur in the sample. We start with the total mass of the sample (15.15g) and subtract the mass of copper (5.27g) and iron (4.61g) to get the mass of sulfur:
Total mass of sample - mass of copper - mass of iron = mass of sulfur
15.15g - 5.27g - 4.61g = 5.27g of sulfur
Next, we convert the masses of copper, iron, and sulfur to moles by dividing by their respective atomic masses:
- Moles of copper = 5.27g Cu / 63.546 amu = 0.0829 moles Cu
- Moles of iron = 4.61g Fe / 55.845 amu = 0.0826 moles Fe
- Moles of sulfur = 5.27g S / 32.065 amu = 0.1642 moles S
To find the simplest whole number ratio, we divide each of the mole values by the smallest mole value obtained:
- Copper: 0.0829 / 0.0826 ≈ 1
- Iron: 0.0826 / 0.0826 = 1
- Sulfur: 0.1642 / 0.0826 = 1.99 ≈ 2
Thus, the empirical formula based on our mole ratio is CuFeS2.