"A" obtained by Ostwald's method involving air oxidation of NH3, upon further air oxidation produces "B". "B" on hydration forms an oxoacid of nitrogen along with evolution of "A". The oxoacid also produces "A" and gives a positive brown ring test.
A
NO2, N2O5
B
NO2, N2O4
C
NO, NO2
D
N2O3, NO2
Answer
Correct answer:C
Step-by-step solution
Standard Method
Given: "A" is obtained in the Ostwald process from air oxidation of NH3. On further oxidation, A gives B. On hydration, B forms an oxoacid of nitrogen along with evolution of A.
Find: The identities of A and B.
In the Ostwald process, ammonia is oxidized to nitric oxide:
4NH3+5O2Pt,500∘C4NO+6H2O
So, A = NO.
Further oxidation of nitric oxide gives nitrogen dioxide:
2NO+O2→2NO2
So, B = NO2.
On hydration, nitrogen dioxide forms nitric acid along with nitric oxide:
3NO2+H2O→2HNO3+NO
The oxoacid formed is nitric acid, which is associated with the brown ring test.
Therefore, the pair is NO,NO2 and the correct option is C.
Discrepancy noted: the solution states "The Correct Option is A", but the worked chemistry and final answer line clearly identify (3)NO,NO2, which corresponds to option C.
Common mistakes
Confusing the first product of the Ostwald process with NO2. This is wrong because ammonia is first oxidized to NO, and only then NO undergoes further oxidation. Start with the industrial process sequence correctly.
Assuming hydration of NO2 gives only one oxide or only one acid product. This is wrong because the given reaction produces nitric acid along with evolution of NO. Use the reaction 3NO2+H2O→2HNO3+NO.
Linking the brown ring test to the wrong nitrogen oxide instead of the oxoacid formed. This is wrong because the test is used for nitrate-containing species, supporting identification of nitric acid. First identify the acid formed after hydration, then use the test clue.
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