What are the spectator ions in 2H+ + SO42- + Ca2+ + 21- → CaSO4 + 2H+ + 21-

H⁺ and I⁻ ions

Explanation:

Spectator ions are ions that appear in a solution but do not take part in the chemical reaction. This ions remain unchanged before and after the chemical equation.

From the equation:

2H⁺ + SO₄²⁻ + Ca²⁺ + 2I⁻   ⇒   CaSO₄ + 2H⁺ + 2I⁻

We can see that both H⁺ and I⁻ ions remain unchanged as the reaction occurs, therefore they are spectator ions. Removing the spectator ions gives a net ionic equation:

SO₄²⁻ + Ca²⁺    ⇒   CaSO₄

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