Iron(II) ions treated with aqueous ammonia yield which observation?

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Multiple Choice

Iron(II) ions treated with aqueous ammonia yield which observation?

Explanation:
When a metal ion is treated with a base like ammonia, it often forms an insoluble metal hydroxide that appears as a precipitate. For iron(II) ions, the base raises the pH enough to cause Fe2+ to form iron(II) hydroxide, Fe(OH)2. This compound is pale green in color and, unlike some other hydroxides, it does not dissolve in excess ammonia because Fe2+ doesn’t form a stable ammine complex with hydroxide in these conditions. The solid remains as a green precipitate. If left in air, Fe(OH)2 can slowly oxidize to Fe(OH)3, which is brown, so you may see a color change over time. So the key observation is a green precipitate of Fe(OH)2 that is insoluble in excess ammonia.

When a metal ion is treated with a base like ammonia, it often forms an insoluble metal hydroxide that appears as a precipitate. For iron(II) ions, the base raises the pH enough to cause Fe2+ to form iron(II) hydroxide, Fe(OH)2. This compound is pale green in color and, unlike some other hydroxides, it does not dissolve in excess ammonia because Fe2+ doesn’t form a stable ammine complex with hydroxide in these conditions. The solid remains as a green precipitate. If left in air, Fe(OH)2 can slowly oxidize to Fe(OH)3, which is brown, so you may see a color change over time. So the key observation is a green precipitate of Fe(OH)2 that is insoluble in excess ammonia.

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