Answer :
Sodium sulfate, Na₂SO₄, is a strong electrolyte. It means that it dissociates into 2 Na⁺ ions and 1 SO₄⁻ ion when dissolved in water. So, for every 1 mole of Na₂SO₄, there is an equivalent amount of 2 mol Na⁺ ions. The solution is as follows:
Moles of Na⁺ = (1.27 mol Na₂SO₄/L)*(1 L/1000 mL)*(343 mL)*(2 mol Na⁺/1 mol Na₂SO₄)
Moles of Na⁺ = 0.87 mol
Moles of Na⁺ = (1.27 mol Na₂SO₄/L)*(1 L/1000 mL)*(343 mL)*(2 mol Na⁺/1 mol Na₂SO₄)
Moles of Na⁺ = 0.87 mol