Question

when only one atom undergoes change in oxidation state but goes into two products having same oridation state vas a result of either oxidation or reduction.

Answer 1

The provided definition describes a redox reaction where a single element changes its oxidation state and is then incorporated into two different product compounds or ions, maintaining the same new oxidation state in both products. The change in oxidation state must be a net oxidation or a net reduction. An example is the reduction of dichromate ion: In $Cr_2O_7^{2-}$, Cr has an oxidation state of +6. In the products, $Cr^{3+}$ and $CrCl_3$, Cr has an oxidation state of +3 in both. Since Cr changes from +6 to +3, it undergoes reduction, forming two different products where its oxidation state is consistently +3.

Answer 2

The question defines a specific type of redox reaction and provides an example with some calculations. The task is to explain this definition and illustrate it with the given example.

Explanation of the Definition: This definition describes a scenario in a chemical reaction where:

1. Only one type of atom (element) undergoes a change in its oxidation state.
2. This particular atom, after changing its oxidation state, is incorporated into two different chemical products.
3. Crucially, in both of these product species, the atom possesses the same new oxidation state.
4. The overall change in oxidation state for this atom must be either a net oxidation (increase in oxidation state) or a net reduction (decrease in oxidation state). This means the atom is not simultaneously oxidized and reduced (which would be disproportionation).

Example from the image: The example provided is related to the reduction of the dichromate ion ($Cr_2O_7^{2-}$). The reaction shown is: $Cr_2O_7^{2-} \rightarrow Cr^{3+} + CrCl_3$

Let's analyze the oxidation states of Chromium (Cr) in the reactant and products:

1. Oxidation state of Cr in the reactant ($Cr_2O_7^{2-}$): Let the oxidation state of Cr be $x$. Oxygen typically has an oxidation state of -2. The overall charge of the ion is -2. $2(x) + 7(-2) = -2$ $2x - 14 = -2$ $2x = 12$ $x = +6$ So, Chromium in $Cr_2O_7^{2-}$ is in the +6 oxidation state.

2. Oxidation state of Cr in the first product ($Cr^{3+}$): The oxidation state of a monoatomic ion is equal to its charge. So, Chromium in $Cr^{3+}$ is in the +3 oxidation state.

3. Oxidation state of Cr in the second product ($CrCl_3$): Let the oxidation state of Cr be $y$. Chlorine (Cl) typically has an oxidation state of -1 in halides. The compound is neutral. $y + 3(-1) = 0$ $y - 3 = 0$ $y = +3$ So, Chromium in $CrCl_3$ is also in the +3 oxidation state.

Verification against the definition:

• "only one atom undergoes change in oxidation state": Yes, only Chromium changes its oxidation state (from +6 to +3).
• "but goes into two products": Yes, Chromium from the reactant ($Cr_2O_7^{2-}$) forms two distinct products: $Cr^{3+}$ and $CrCl_3$.
• "having same oxidation state": Yes, in both products ($Cr^{3+}$ and $CrCl_3$), Chromium is in the +3 oxidation state.
• "as a result of either oxidation or reduction": The oxidation state of Chromium decreases from +6 to +3. This is a reduction.

Thus, the given example perfectly illustrates the defined type of redox reaction. The numerical calculations ($2x = 142-2$, $x = 16$, $m = 2/3-61$) shown in the image are extraneous and not related to the chemical concept being explained.

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• Explanation of the solution: The problem defines a specific type of redox reaction: one atom changes oxidation state and forms two products where it has the same new oxidation state (either by oxidation or reduction). The given example, $Cr_2O_7^{2-} \rightarrow Cr^{3+} + CrCl_3$, illustrates this. In $Cr_2O_7^{2-}$, Cr is +6. In both products, $Cr^{3+}$ and $CrCl_3$, Cr is +3. Since +6 reduces to +3, this is a reduction, fitting the definition.