Final answer:
Mixing a typical iodine ion with a typical barium ion forms barium iodide (BaI2). Sodium sulfate can be used to precipitate barium ions from water, forming barium sulfate (BaSO4) as the precipitate.
Step-by-step explanation:
When a typical iodine ion (I−, with an oxidation state of −1) is mixed with a typical barium ion (Ba2+, with an oxidation state of +2), the resulting compound formed is barium iodide (BaI2). This is due to the fact that the barium ion requires two iodine ions to balance the electrical charges, thereby creating a neutral compound. In a chemical equation, it can be represented as Ba2+ + 2I− → BaI2.
To address the Check Your Learning question, sodium sulfate could be used to precipitate the barium ion (Ba2+) in a water sample. The resulting precipitate would be barium sulfate (BaSO4).