Here's how to write the equation for the reaction of iron(III) phosphate with sodium sulfate to produce iron(III) sulfate and sodium phosphate:

1. Write the formulas for the reactants and products:

* Iron(III) phosphate: FePO₄

* Sodium sulfate: Na₂SO₄

* Iron(III) sulfate: Fe₂(SO₄)₃

* Sodium phosphate: Na₃PO₄

2. Balance the equation:

FePO₄ + Na₂SO₄ → Fe₂(SO₄)₃ + Na₃PO₄

To balance the equation, we need:

* 2 FePO₄

* 3 Na₂SO₄

* 1 Fe₂(SO₄)₃

* 2 Na₃PO₄

3. The balanced chemical equation is:

2 FePO₄ + 3 Na₂SO₄ → Fe₂(SO₄)₃ + 2 Na₃PO₄