Question

3. What is the molar mass of Fe2(SO4)3 4. How many atoms are in 28.0 grams of Calcium?

Answer 1

3)

Atomic mass of Fe = 55.85

Atomic mass of Oxygen = 16 g / mol

Atomic mass of Sulfur = 32.06 g / mol

The molar mass of Fe₂(SO₄)₃ = 2(55.85) + 3(32.06) + 12(16.00)

= 111.7 + 96.18 + 192.0

= 399.88 g / mol

4)

Given that,

Mass = 28 g

Number of moles = Mass / molar mass

= 28 g / 40.078 g / mol

= 0.698 moles

We know that, 1 mol of the element contains 6.022 x 10²³ atoms

number of atoms = 0.698 x 6.022 x 10²³

= 4.20 x 10²³ atoms