Question

Determine the mass in grams of Li⁺ (6.941 g/mol) in 25.0 g of Li₂SO₄ (109.94 g/mol)

Answer 1

The compound dissociates as the following:

Li₂SO₄ = 2Li⁺ + SO₄^2-

From here, the mass of lithium ions equals:

m(Li⁺) = m(Li₂SO₄) × 2 × Mr(Li⁺) / Mr(Li₂SO₄) = 25.0 g × 2 × 6.941 g/mol / 109.94 g/mol = 3.16 g

Answer: 3.16 g