A given sample of Na2SO4 contains 6.02×10^22 SO4²- ions. Calculate number of Na+ ions, number of formula units, weight of the sample

Answer 1

Looking at what happens when Na₂SO₄ is placed in water:

Na₂SO₄ ==> 2Na⁺ + SO₄^2-

Notice there are TWO MOLES of Na⁺ for each mole of Na₂SO₄

Finding number of Na⁺ ions:

6.02x10²² SO₄^2- ions x 2 Na⁺ ions / 1 SO₄^2- ion = 1.20x10²³ Na⁺ ions

Finding number of formula units:

6.02x10²² SO₄^2- ions x 1 mol Na₂SO₄ / 6.02x10²³ SO₄^2- ions x 6.02x10²³ form.u. / mol = 6.02x10²²

formula units

Finding weight (mass) of sample:

molar mass 6.02x10²² SO₄^2- ions = 142 g / mol

6.02x10²² SO₄^2- ions x 1 mol Na₂SO₄ / 6.02x10²³ SO₄^2- ions x 142 g / mol = 14.2 g Na₂SO₄