You can't directly add something to sodium hydroxide (NaOH) to get sulfate (SO₄²⁻) and water (H₂O). Here's why:

* Sulfate (SO₄²⁻) is an anion: It's a negatively charged ion. Sodium hydroxide is a strong base. Reactions between bases and anions are not typical.

* You need a source of sulfur: To get sulfate, you need a compound containing sulfur. Sodium hydroxide itself doesn't contain sulfur.

Here's how you could get sulfate and water from sodium hydroxide:

1. React sodium hydroxide with sulfuric acid (H₂SO₄): This is a classic acid-base neutralization reaction.

```

2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

```

* Sodium hydroxide (NaOH) reacts with sulfuric acid (H₂SO₄) to produce sodium sulfate (Na₂SO₄) and water (H₂O).

Important Note: This reaction is highly exothermic (releases a lot of heat). It should be carried out with caution, using appropriate safety equipment.