1. Calculate the moles of Na₂SO₄:

* Molarity (M) = moles of solute / liters of solution

* We have 0.850 M Na₂SO₄ and 325 mL (which is 0.325 L).

* Rearrange the formula to solve for moles: moles = Molarity * liters

* moles of Na₂SO₄ = 0.850 M * 0.325 L = 0.27625 moles

2. Determine the moles of sodium ions (Na⁺):

* Each formula unit of Na₂SO₄ contains 2 sodium ions (Na⁺).

* moles of Na⁺ = 2 * moles of Na₂SO₄ = 2 * 0.27625 moles = 0.5525 moles

3. Calculate the number of sodium ions:

* Use Avogadro's number (6.022 x 10²³ ions/mole) to convert moles to ions.

* Number of Na⁺ ions = 0.5525 moles * (6.022 x 10²³ ions/mole) = 3.32 x 10²³ Na⁺ ions

Therefore, there are approximately 3.32 x 10²³ sodium ions present in 325 mL of 0.850 M Na₂SO₄ solution.