ExamHabit
Practise free

JEE Main 2023 · 29 Jan · Shift 1

JEE Main 2023 Chemistry question on p-Block Elements

"A" obtained by Ostwald's method involving air oxidation of NH3\text{NH}_3, 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 positive brown ring test.

Identify A and B, respectively.
  1. A.
    NO2,N2O5\text{NO}_2, \text{N}_2\text{O}_5
  2. B.
    NO,NO2\text{NO}, \text{NO}_2
  3. C.
    NO,N2O4\text{NO}, \text{N}_2\text{O}_4
  4. D.
    N2O3,NO2\text{N}_2\text{O}_3, \text{NO}_2
Show answer and solution

Correct option: B

Solution

Ostwald's process oxidizes NH₃ to NO (compound A). Further air oxidation of NO gives NO₂ (compound B): 2NO + O₂ → 2NO₂. When NO₂ undergoes hydration (disproportionation), it forms HNO₃ and regenerates NO: 3NO₂ + H₂O → 2HNO₃ + NO, consistent with "B on hydration forms an oxoacid along with evolution of A." HNO₃ itself decomposes to release NO₂ but more relevantly, dilute HNO₃ gives the brown ring test (reaction with FeSO₄ to form [Fe(H₂O)₅NO]²⁺), and HNO₃ on strong heating produces NO — matching "the oxoacid also produces A." Hence A = NO and B = NO₂.

[JEE Main 2023 · 29 Jan · Shift 1]

Practise p-Block Elements the way it is asked

A timed set of real JEE Main p-Block Elements questions, graded as the exam grades. No sign-up.

Start a p-Block Elements test

More: all JEE Main p-Block Elements questions · JEE Main 2023 · Chemistry chapter list