Question

Select the options in which the element given in the square brackets has an oxidation number of +5.

• A. $H_2\left[C\right]O_3$
• B. $\left[S\right]O_2$
• C. $H\left[N\right]O_3$
• D. $H_3\left[P\right]O_4$

Answer 1

Answer: (C), (D)

The correct options are
C

$H\left[N\right]O_3$

D

$H_3\left[P\right]O_4$

Let's check the oxidation number of all the elements given in the small brackets.

(1) For $H_2\left[C\right]O_3$, let oxidation number of C be $x$.

$+2+x+3\times (-2)=0$ we get the oxidation number of C = +4.

(2) For $\left[S\right]O_2$, let oxidation number of S be $x$.

$x+2\times (-2)=0$ we get the oxidation number of S = +4.

(3) For $H_3\left[P\right]O_4$, let oxidation number of P be $x$.

$3\times (+1)+x+4\times (-2)=0$ we get the oxidation number of P = +5.

(4) For $H\left[N\right]O_3$, let oxidation number of N be $x$.

$+1+x+3\times (-2)=0$ we get the oxidation number of N = +5.

So the oxidation number of P from $H_3\left[P\right]O_4$ and N from $H\left[N\right]O_3$ is equal to +5. So both the compounds are the correct answer.