pBlock ElementsII 1 Question 4

4. The correct order of the oxidation states of nitrogen in NO, $\mathrm{NO} _{2}, \mathrm{NO} _{2}$ and $\mathrm{N} _{2} \mathrm{O} _{3}$ is

(2019 Main, 9 April I)

(a) $\mathrm{NO} _{2}<\mathrm{NO}<\mathrm{N} _{2} \mathrm{O} _{3}<\mathrm{N} _{2} \mathrm{O}$

(b) $\mathrm{N} _{2} \mathrm{O}<\mathrm{NO}<\mathrm{N} _{2} \mathrm{O} _{3}<\mathrm{NO} _{2}$

(c) $\mathrm{O} _{2}<\mathrm{N} _{2} \mathrm{O} _{3}<\mathrm{NO}<\mathrm{N} _{2} \mathrm{O}$

(d) $\mathrm{N} _{2} \mathrm{O}<\mathrm{N} _{2} \mathrm{O} _{3}<\mathrm{NO}<\mathrm{NO} _{2}$

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Answer:

Correct Answer: 4. (b)

Solution:

  1. The correct increasing order of oxidation state of nitrogen for nitrogen oxides is

$ \stackrel{+1}{\mathrm{N}} _{2} \mathrm{O}<\stackrel{+2}{\mathrm{N}} \mathrm{O}<\stackrel{+3}{\mathrm{N}} _{2} \mathrm{O} _{3}<\stackrel{+4}{\mathrm{N}} \mathrm{O} _{2} $

  • Oxidation state of $\mathrm{N}$ in $\mathrm{N} _{2} \mathrm{O}$ is

$2(x)-2=0 $

$x=+\frac{2}{2}=+1$

  • Oxidation state of $\mathrm{N}$ in $\mathrm{NO}$ is

$x-2 =0 $

$x =+2$

  • Oxidation state of $\mathrm{N}$ in $\mathrm{N} _{2} \mathrm{O} _{3}$ is

$2 x+3(-2)=0 $

$x=\frac{6}{2}=3$

  • Oxidation state of $\mathrm{N}$ in $\mathrm{NO} _{2}$ is

$x+2(-2) =0 $

$x-4 =0 $

$x =+4$