NEET Practice Questions (MCQs) with Answers & Solutions

The acidic character of oxyacids increases with increase in oxidation number. The acidity of oxyacids of chlorine decreases in the following order.

           $\mathrm{H}\stackrel{+7}{\mathrm{Cl}}{\mathrm{O}}_4>\mathrm{H}\stackrel{+5}{\mathrm{Cl}}{\mathrm{O}}_3>\mathrm{H}\stackrel{+3}{\mathrm{Cl}}{\mathrm{O}}_2>\mathrm{H}\stackrel{+1}{\mathrm{Cl}}\mathrm{O}$

So relative acidic character increases

${\left[\stackrel{\text{*\hspace{0.17em}\hspace{0.17em}}}{\mathrm{Cr}}{\left({\mathrm{H}}_2\mathrm{O}\right)}_4{\mathrm{Cl}}_2\right]}^{+}$

$x+0+2\hspace{0.17em}(-1)=+\hspace{0.17em}1$; $x-2=+\hspace{0.17em}1$

x = +3 for Cr in complex. 

$\stackrel{0\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}{B{r}_2}\to \stackrel{+5\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}{Br{O}_3^{-}}$, in this reaction oxidation state change from 0 to + 5.  

$\text{K[}\stackrel{\ast }{C}o{\left(CO\right)}_4]$

$1+x+0=0;\hspace{0.17em}\hspace{0.17em}x=-1$. 

If any central metal atom combined with corbonyl group than central metal atom shows always zero oxidation state.

$S{n}^{2+}\to S{n}^{4+}+2e^{-}$  

The chemical structure of H₂S₂O₈ is as follows:-

$H-O-\underset{O}{\overset{O}{\underset{\left|\right|}{\overset{\left|\right|}{S}}}}-O-O-\underset{O}{\overset{O}{\underset{\left|\right|}{\overset{\left|\right|}{S}}}}-O-H$

So the oxidation number of S should be :

$\underset{(for\hspace{0.17em}\hspace{0.17em}H)}{2\times (+1)}+\underset{(for\hspace{0.17em}\hspace{0.17em}S)}{2\times X}+\underset{(for\hspace{0.17em}\hspace{0.17em}O)}{6\times (-2)}+\underset{(for\hspace{0.17em}\hspace{0.17em}O-O)}{2\times (-1)}=0$ or X = +6.

In hydrazoic acid (N₃H) nitrogen shows $-\frac{1}{3}$ oxidation state.

$\stackrel{\ast \hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}{N_{3}H}$

$3x+1=0$, 3x = –1, $x=-\frac{1}{3}$. 

${\text{[Cr}{{\text{(NH}}_3)}_4{\mathrm{Cl}}_2]}^{+}$

$x+4\times \left(0\right)-2=1$

⇒ $x+0-2=1$

⇒ x = 1 + 2 = + 3.

In this  complex  iron  is a central metal atom showing  +1 oxidation state.becoz NO is showing +1 charge here.