1. Understand the Chemical Formula:

* Na₂SO₄ represents sodium sulfate. The subscript "2" next to the Na indicates that there are two moles of sodium atoms for every one mole of sodium sulfate.

2. Use the Mole Ratio:

* The mole ratio from the formula is 2 moles Na : 1 mole Na₂SO₄.

3. Calculate Moles of Sodium:

* Since you have 5.25 moles of Na₂SO₄, multiply this by the mole ratio to find the moles of sodium:

5.25 moles Na₂SO₄ * (2 moles Na / 1 mole Na₂SO₄) = 10.5 moles Na

Therefore, there are 10.5 moles of sodium in 5.25 moles of Na₂SO₄.