A sample with a mass of 9.572 g consists of 26.58% potassium, 35.35% chromium, and 28.07% oxygen. How many atoms of K and Cr are there in the empirical formula?
To find the number of atoms of K and Cr in the empirical formula, we first need to determine the molar mass of each element.
1. Convert the percentages to grams:
- 26.58% potassium = 9.572 g x 0.2658 = 2.544 g K
- 35.35% chromium = 9.572 g x 0.3535 = 3.382 g Cr
- 28.07% oxygen = 9.572 g x 0.2807 = 2.684 g O
2. Calculate the moles of each element:
- Moles of K = 2.544 g / 39.10 g/mol (molar mass of K) = 0.0651 mol K
- Moles of Cr = 3.382 g / 51.996 g/mol (molar mass of Cr) = 0.0651 mol Cr
3. Determine the ratio of moles to find the empirical formula:
- Since the moles of K and Cr are equal, the empirical formula is KCr.
4. Calculate the number of atoms of K and Cr in one formula unit:
- Since there are 0.0651 moles of K and Cr in one formula unit, there are 6.02 x 10^23 atoms/mol x 0.0651 mol = 3.72 x 10^22 atoms of each element in the empirical formula.