Different Oxidation States of Iron Comparison Standards Solution FeSO4) FeCl(oa) Iron ion present (+2/+3) Interpret how the KSCN allows you to better tell which iron ion you have. Reaction 1 Balance each half-reaction including electrons, then balance the overall net ionic equation. Give the oxidation state for each atom in the equation. Ox: Fe? Red: NO, Net: What ion/molecule contains the element that gets oxidized? What is the oxidizing agent in the above reaction?
The Correct Answer and Explanation is :
Balanced Half-Reactions and Overall Net Ionic Equation
Oxidation Half-Reaction (Fe²⁺ to Fe³⁺):
The oxidation reaction involves iron (Fe²⁺) being oxidized to Fe³⁺ by losing one electron.
[
\text{Fe}^{2+} \rightarrow \text{Fe}^{3+} + e^-
]
Reduction Half-Reaction (NO₃⁻ to NO):
In the reduction half-reaction, nitrate ion (NO₃⁻) is reduced to nitrogen monoxide (NO) by gaining electrons. To balance the equation, we need to account for the hydrogen ions (H⁺) that balance the overall charges and atoms.
[
\text{NO}_3^- + 4\text{H}^+ + 3e^- \rightarrow \text{NO} + 2\text{H}_2\text{O}
]
Overall Net Ionic Equation:
The overall reaction involves combining the two half-reactions, ensuring that electrons are balanced. The number of electrons lost in the oxidation half-reaction is 1, and in the reduction half-reaction is 3. To balance this, we multiply the oxidation reaction by 3 and the reduction reaction by 1.
[
3 \text{Fe}^{2+} + \text{NO}_3^- + 12\text{H}^+ \rightarrow 3\text{Fe}^{3+} + \text{NO} + 6\text{H}_2\text{O}
]
Oxidation States and Key Points:
- Fe: In Fe²⁺, the oxidation state of iron is +2, and in Fe³⁺, it is +3.
- Nitrate Ion (NO₃⁻): In NO₃⁻, nitrogen has an oxidation state of +5, and in NO, nitrogen has an oxidation state of +2.
- Oxidized Species: Fe²⁺ is the element being oxidized (it loses electrons to become Fe³⁺).
- Reducing Agent: Fe²⁺ is the reducing agent because it donates electrons to the nitrate ion (NO₃⁻).
- Oxidizing Agent: NO₃⁻ is the oxidizing agent because it accepts electrons, reducing to NO.
Role of KSCN:
KSCN (Potassium thiocyanate) helps in determining the iron oxidation state because thiocyanate ions react with Fe³⁺ ions to form a reddish-brown complex, while Fe²⁺ does not form this complex. This visual test can distinguish between Fe²⁺ and Fe³⁺ ions in a solution. The formation of the red complex indicates the presence of Fe³⁺, whereas the absence of the color change suggests Fe²⁺. Therefore, KSCN serves as a qualitative indicator of the iron oxidation state in a given solution.