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Question: **Question 37:** In liquid N$_2$O$_4$ as a solvent...

Question 37: In liquid N2_2O4_4 as a solvent

A

NOBr acts as an acid

B

Ba(NO3_3)2_2 acts as a base

C

N-N bond length order N2_2H4_4 > N2_2O4_4

D

Reaction between NOCl and NaNO3_3 is an acid base reaction

Answer

A, B, D

Explanation

Solution

The question asks us to identify the correct statements regarding liquid N2_2O4_4 as a solvent.

Liquid N2_2O4_4 undergoes autoionization as follows: N2O4⇌NO+(nitrosonium ion)+NO3−(nitrate ion)\text{N}_2\text{O}_4 \rightleftharpoons \text{NO}^+ \text{(nitrosonium ion)} + \text{NO}_3^- \text{(nitrate ion)}

In this solvent system:

  • An acid is a substance that increases the concentration of NO+^+ ions.
  • A base is a substance that increases the concentration of NO3−_3^- ions.
  • An acid-base reaction (neutralization) involves the reaction of an acid and a base to form the solvent and a salt.

Let's analyze each option:

A. NOBr acts as an acid NOBr dissociates in liquid N2_2O4_4 as: NOBr⇌NO++Br−\text{NOBr} \rightleftharpoons \text{NO}^+ + \text{Br}^- Since NOBr produces NO+^+ ions, it acts as an acid in this solvent system. Therefore, statement A is correct.

B. Ba(NO3_3)2_2 acts as a base Ba(NO3_3)2_2 dissociates in liquid N2_2O4_4 as: Ba(NO3)2⇌Ba2++2NO3−\text{Ba(NO}_3\text{)}_2 \rightleftharpoons \text{Ba}^{2+} + 2\text{NO}_3^- Since Ba(NO3_3)2_2 produces NO3−_3^- ions, it acts as a base in this solvent system. Therefore, statement B is correct.

C. N-N bond length order N2_2H4_4 > N2_2O4_4

  • In N2_2H4_4 (hydrazine), the N-N bond is a pure single bond. Its bond length is approximately 1.45 Å.
  • In N2_2O4_4 (dinitrogen tetroxide), the N-N bond is also a single bond, but it is unusually long due to steric repulsion between the oxygen atoms on the two NO2_2 groups and weak N-N bond. Its bond length is approximately 1.75 Å.

Comparing the bond lengths: 1.75 Å (N2_2O4_4) > 1.45 Å (N2_2H4_4). Therefore, the correct order is N2_2O4_4 > N2_2H4_4. The statement N2_2H4_4 > N2_2O4_4 is incorrect. Therefore, statement C is incorrect.

D. Reaction between NOCl and NaNO3_3 is an acid base reaction

  • NOCl dissociates as: NOCl⇌NO++Cl−\text{NOCl} \rightleftharpoons \text{NO}^+ + \text{Cl}^-. Since it produces NO+^+, NOCl is an acid.
  • NaNO3_3 dissociates as: NaNO3⇌Na++NO3−\text{NaNO}_3 \rightleftharpoons \text{Na}^+ + \text{NO}_3^-. Since it produces NO3−_3^-, NaNO3_3 is a base. The reaction between NOCl and NaNO3_3 is: NOCl (acid)+NaNO3(base)→NaCl+N2O4(solvent)\text{NOCl (acid)} + \text{NaNO}_3 \text{(base)} \rightarrow \text{NaCl} + \text{N}_2\text{O}_4 \text{(solvent)} This is a typical acid-base (neutralization) reaction in the N2_2O4_4 solvent system, where an acid and a base react to form a salt and the solvent. Therefore, statement D is correct.

Based on the analysis, statements A, B, and D are correct.