MCQ
$Fe(OH)_2$ is precipitated from $Fe(II)$ solutions as a while solid but turns dark green and then brown due to the formation of
- A$Fe(OH)_2$ and $Fe(OH)_3$
- Bonly $Fe(OH)_3$
- ✓$Fe_2O_3. (H_2O)_n$
- D$Fe_2O_3 ·2H_2O$
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$E ^0\left( Fe ^{3+} . Fe ^{2+}\right)=+0.77 V $
$E ^0\left( Fe ^{2+} . Fe \right)=-0.44 V $
$E ^{\circ}\left( Cu ^{2+} . Cu \right)=+0.34 V $
$E ^0\left( Cu ^{+} . Cu \right)=+0.52 V $
$E ^{\circ}\left( O _2( g )+4 H ^{+}+4 e ^{-} \rightarrow 2 H _2 O \right)=+1.23 V $
$E ^{\circ}\left( O _2( g )+2 H _2 O +4 e ^{-} \rightarrow 4 OH \right)=+0.40 V $
$E ^0\left( Cr ^{3+} . Cr \right)=-0.74 V $
$E ^{\circ}\left( Cr ^{2+} . Cr \right)=-0.91 V$
Match $E ^{\circ}$ of the rebox pair in List $I$ with the values given in List $II$ and select the correct answer using the code given below the lists:
| List $I$ | List $II$ |
| $P.$ $\quad E ^{\circ}\left( Fe ^{3+}, Fe \right)$ | $1.$ $\quad-0.18 V$ |
| $Q.$ $\quad E ^{\circ}\left(4 H _2 O \rightleftharpoons 4 H ^{+}+4 OH ^{-}\right)$ | $2.$ $\quad-0.4 V$ |
| $R.$ $\quad E ^{\circ}\left( Cu ^{2+}+ Cu \rightarrow 2 Cu ^{+}\right)$ | $3.$ $\quad-0.04 V$ |
| $S.$ $\quad E ^{\circ}\left( Cr ^{3+}, Cr ^{+2}\right)$ | $4.$ $\quad-0.83 V$ |
Codes: $ \quad P \quad Q \quad R \quad S $
$(1)$ $(CH_3)_3 {\bar{\ddot{C}}}$
$(2)$ ${(C{H_3})_2}{\bar {\ddot {CH}}}$
$(3) $ $C{H_3}{\bar{\ddot{C{H_2}}}}$
$(4)$ ${C_6}{H_5}{\bar{\ddot{C{H_2}}}}$ is
$(1)$ It is reduced to methyl phenyl carbinol by sodium and ethanol
$(2)$ It is oxidised to benzoic acid with acidified $KMn{O_4}$
$(3)$ It does not undergo iodoform electrophilic substitution like nitration at meta position
$(4)$ It does not undergo iodoform reaction with iodine and alkali
$F{e^{ + 2 }} + 2{e^ - }\, \to \,Fe\,;\,\,\,\,{E^o} = - 0.440\,V$
$F{e^{ + 3 }} + 3{e^ - }\, \to \,Fe\,;\,\,\,\,{E^o} = - 0.036\,V$The standard electrode potential $({E^o})$ for$F{e^{ + 3 }} + {e^ - } \to \,F{e^{ + 2 }}$ is .............. $\mathrm{V}$
Step$-1$ : ${\text{A + E }} \rightleftharpoons AE$ (fast)
Step$-2$ :${\text{AE + A }} \to {A_2} + E$ (slow)
Step$-3$ :${{\text{A}}_2}{\text{ + B }} \to {\text{D}}$ (fast)
what rate law best agrees with this mechanism