MCQ
Given :
$E^o_{Fe^{3+} /Fe} = -0.036\,V,$ $E^o _{Fe^{2+} /Fe} = -0.439\,V$
The value of standard electrode potential for the change,
$Fe^{3+} (aq) + e^- \rightarrow Fe^{2+} (aq)$ will be ........ $V$.
- A$0.385$
- ✓$0.770$
- C$-0.270$
- D$-0.072$
✓
Answer
Correct option: B.
$0.770$
b
$F e^{3+}+3 e^{-} \rightarrow F e, E^{o}_{F e^{3} 4 / F e}$
$F e^{3+}+3 e^{-} \rightarrow F e, E^{o}_{F e^{3} 4 / F e}$
$=-0.036 V \ldots(i)$
$F e^{2+}+2 e^{-} \rightarrow F e, E^{\circ}_{F e^{2} / / F e}$
$=-0.439 V \ldots(i i)$
we have to calculate
$F e^{3+}+e^{-} \rightarrow F e^{2+}, \Delta G=?$
To obtain this equation subtract equ $( ii )$ from $( i )$ we get
$F e^{3+}+e^{-} \rightarrow F e^{2+} \ldots(i i i)$
As we know that $\Delta G=-n F E$
Thus for reaction ( iii)
$\Delta G=\Delta G_{1}-\Delta G$
$-n F E^{\circ}=-n F E_{1}-\left(-n F E_{2}\right)$
$-n F E^{\circ}=n F E_{2}-n F E_{1}$
$-1 F E^{\circ}=2 \times 0.439 F-3 \times 0.036 F$
$- F E^{\circ}=0.770 F$
$\therefore \quad E^{\circ}=-0.770 V$
$O^{-}>F^{-}>N a^{+}>M g^{++}>A l^{3+}$
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
The nature of oxide $\left(\mathrm{TeO}_{2}\right)$ and hydride $\left(\mathrm{TeH}_{2}\right)$ formed by Te , respectively are :
→The compound $A$ on treatment with $Na$ gives $B$, and with $\mathrm{PCl}_{5}$ gives $\mathrm{C} . \mathrm{B}$ and $\mathrm{C}$ react together to give diethyl ether. $\mathrm{A}, \mathrm{B}$ and $\mathrm{C}$ are in the order
→Upon heating $KClO_3$ in the presence of catalytic amount of $MnO_2$, a gas $W$ is formed. Excess amount of $W$ reacts with white phosphorus to give $X$. The reaction of $X$ with $HNO_3$ gives $Y$ and $Z$.
→($1$) $W$ and $\mathbf{X}$ are, respectively
$[A]$ $O_3$ and $P_4 O_6$ $[B]$ $O_2$ and $P_4 O_6$ $[C]$ $O_2$ and $P_4 O_{10}$ $[D]$ $O_3$ and $P_4 O_{10}$
($2$) $Y$ and $Z$ are, respectively
$[A]$ $N_2 O_3$ and $\mathrm{H}_3 \mathrm{PO}_4$
$[B]$ $N_2 O_5$ and $\mathrm{HPO}_3$
$[C]$ $N_2 O_4$ and $HPO_3$
$[D]$ $N_2 O_4$ and $H_3 PO_3$
Give the answer of quetion ($1$) and ($2$)
The tests performed on compound $X$ and their inferences are
→| Test | Interference |
| $(a)$ $2, 4-DNP$ test | Colorued precipitate |
| $(b)$ Iodoform test | Yellow precipitate |
| $(c)$ Azo-dye test | No dye formation |
Compound $‘X’$ is
Major product $(A)$ is
→Identify the incorrect statement in the following
Reaction between benzaldehyde and acetophenone in presence of dilute $NaOH$ is known as
→Which of the following statement is not correct?
To prevent corrosion, iron pipes carrying drinking water are covered with zinc. The process involved is
Among the following which one is a wrong statement?