Video: Predicting the Product of the Reaction of FeCl₃, NH₃, and Water

Which of the following is one of the products obtained from the given reaction? _ FeCl₃ + _ NH₃ + _ H₂O ⟶ _ [A] FeH₃ [B] FeN [C] Fe(OH)₃ [D] Fe(NO₃)₃ [E] Fe


Video Transcript

Which of the following is one of the products obtained from the given reaction? Blank FeCl₃ plus blank NH₃ plus blank H₂O react to form blank. A) FeH₃, B) FeN, C) Fe(OH)₃, D) Fe(NO₃)₃, or E) Fe.

Let’s quickly go through the names. A, FeH₃, is iron(III) hydride; B, FeN, is iron(III) nitride; C, Fe(OH)₃, is iron(III) hydroxide; D, Fe(NO₃)₃, is iron(III) nitrate; and E, Fe, is iron. FeCl₃ is iron(III) chloride and NH₃ is ammonia. H₂O is obviously water. So the reaction type we’re dealing with is the reaction of metal chloride and ammonia and water. If you’re not sure how a mixture of three things are going to react, you might want to look at them in isolation first. We can borrow a tool from maths with the Venn diagram. Obviously, each of these components on their own, they just kind of do what they always do. They’ll stick around and nothing will change.

Iron chloride is an ionic salt. When mixed with water, it’s just going to dissolve. So we get a solution of iron(III) chloride. Ammonia is a base. It reacts directly with water to form ammonium hydroxide. In an excess of water, we’ll have dissolved ammonium hydroxide. The last overlap of two components is iron chloride and ammonia. But both of these are basic materials, so it’s not clear exactly how they’d interact. But our final destination is the overlap of all three. So we can get there by seeing how the combination of iron chloride and water and water and ammonia interact.

The reaction of an iron(III) salt with ammonia hydroxide is actually a common test. If we had a solution of iron(III) ions and introduced a solution of ammonia, which is also called ammonium hydroxide, we’d see a dirty brown precipitate of iron(III) hydroxide. So when we react together, iron(III) chloride, ammonia, and water. We’d expect our products to be iron(III) hydroxide and ammonium chloride. So of the five products given, the one we would expect to obtain from the given reaction is Fe(OH)₃, iron(III) hydroxide.

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