Answer:
These first and the last are examples of reversible reactions:
- Iodine and chlorine can react to form iodine chloride. At equilibrium, the system contains a mixture of iodine, chlorine, and iodine chloride.
- Hydrogen and nitrogen react to form ammonia. At low pressure, the equilibrium system contains all three substances.
Explanation:
The reactions that end in a quasi complete conversion of the reactants into the products are said that are not reversible reactions.
Most of the chemical reactions do not reach a complete conversion. They seem to stop without getting complete conversion. The reason is that these reactions are reversible. A reversible reaction is that that can be forward (direct reaction) and backward (inverse or reverese reaction). In these cases, when the equilibrium is reached the rates of the forward and reverse reactions are equal, which explain why the reaction seems to stop, and a mixture of products and reactants will remain.
The two examples of reversible reactions given may be represented in this way:
1) Iodine and chlorine can react to form iodine chloride. At equilibrium, the system contains a mixture of iodine, chlorine, and iodine chloride.
- Forward reaction: I₂ (g) + Cl₂ (g) → 2ICl (g)
- Reverse reaction: I₂ (g) + Cl₂ (g) ← 2ICl (g))
- Combined reaction: I₂ (g) + Cl₂ (g) ⇄ 2ICl (g)
The double arrow is used to indicate that the reaction is reversible. In the forward reaction, iodine and chlorine react to form iodine chloride, in the reverse reaction iodine chlorice decomposes to form the substances iodine and chlorine.
2) Hydrogen and nitrogen react to form ammonia. At low pressure, the equilibrium system contains all three substances.
- Forward reaction: 3H₂ (g) + N₂ (g) → 2NH₃ (g)
- Reverse reaction: 3H₂ (g) + N₂ (g) ← 2NH₃ (g)
- Combined reaction: 3H₂ (g) + N₂ (g) ⇄ 2NH₃ (g)
In the foward reaction, hydrogen a nitrogen combine to form amonia, in the reverse reaction ammonia decomposes producing the substances hydrogen and nitrogen.
