An aqueous solution of hydrazine (N2H4) is electrochemically oxidized by O2, thereby releasing chemical energy in the form of electrical energy. One of the products generated from the electrochemical reaction is N2(g).
Choose the correct statement(s) about the above process
Choose the correct statement(s) about the above process
- OH- ions react with N2H4 at the anode to form N2(g) and water, releasing 4 electrons to the anode.
- At the cathode, N2H4 breaks to N2(g) and nascent hydrogen released at the electrode reacts with oxygen to form water.
- At the cathode, molecular oxygen gets converted to OH-
- Oxides of nitrogen are major by-products of the electrochemical process.
The Correct Option is A, C
Approach Solution - 1
1. Oxidation and Reduction Reactions:
We are given the following overall reaction for the electrochemical process:
$ \text{N}_2\text{H}_4 + \text{O}_2 \longrightarrow \text{N}_2 + \text{H}_2\text{O}^{2-} $
2. At the Anode (Oxidation):
The oxidation reaction at the anode is:
$ \text{N}_2\text{H}_4 + 4 \text{OH}^- \longrightarrow \text{N}_2 + 4 \text{H}_2\text{O} + 4 e^- $
3. At the Cathode (Reduction):
The reduction reaction at the cathode is:
$ \text{O}_2 + 2 \text{H}_2\text{O} + 4 e^- \longrightarrow 4 \text{OH}^- $
4. Complete Reaction:
The complete reaction combining both oxidation and reduction is:
$ \text{N}_2\text{H}_4 + \text{O}_2 \longrightarrow \text{N}_2 + 2 \text{H}_2\text{O} $
5. Conclusion:
The correct statements are (A) and (C).
Approach Solution -2
To solve the problem, analyze the electrochemical oxidation of hydrazine (\(N_2H_4\)) by oxygen, focusing on reactions at the anode and cathode and products formed.
1. Anode reaction:
In alkaline medium, hydrazine is oxidized at the anode:
\[
N_2H_4 + 4OH^- \rightarrow N_2(g) + 4H_2O + 4e^-
\]
Hydroxide ions react with hydrazine to form nitrogen gas, water, and release electrons.
Option 1 is correct.
2. Cathode reaction:
Oxygen is reduced at the cathode:
\[
O_2 + 2H_2O + 4e^- \rightarrow 4OH^-
\]
Molecular oxygen gets converted to hydroxide ions.
Option 3 is correct.
3. Option 2 analysis:
Hydrazine does not undergo reduction at the cathode in this process; instead, oxygen is reduced. Nascent hydrogen is not formed.
Option 2 is incorrect.
4. By-products:
Electrochemical oxidation of hydrazine mainly produces nitrogen and water; oxides of nitrogen are not major by-products.
Option 4 is incorrect.
Final Answer:
Options 1 and 3 are correct.
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