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Byju's Answer

Standard XII

Chemistry

Reactivity Trends (Group 2)

For M2+/M and...

Question

For $M^{2 +} / M$ and $M^{3 +} / M^{2 +}$ systems the $E^{\circ}$ values for some metals are as follows:

$C r^{2 +} / C r$ $- 0.9 V$ $C r^{3 +} / C r^{2 +}$ $- 0.4 V$

$M n^{2 +} / M n$ $- 1.2 V$ $M n^{3 +} / M n^{2 +}$ $+ 1.5 V$

$F e^{2 +} / F e$ $- 0.4 V$ $F e^{3 +} / F e^{2 +}$ $+ 0.8 V$

Choose the correct statements:

C r^{3 +}

can be reduced to

C r^{2 +}

easily

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M n^{3 +}

can be reduced to

M n^{2 +}

easily

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F e^{3 +}

is more stable than

M n^{3 +}

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F e^{3 +}

is less stable than

C r^{3 +}

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Solution

The correct option is D $F e^{3 +}$ is less stable than $C r^{3 +}$
(a) $C r^{3 +} / C r^{2 +}$ has negative potential. Hence, $C r^{3 +}$ cannot be reduced to $C r^{2 +}$ .
(b) $M n^{3 +} / M n^{2 +}$ has a large positive reduction potential. Hence, $M n^{3 +}$ can be easily reduced to $M n^{2 +}$ .
(c) and (d) $F e^{3 +} / F e^{2 +}$ has small positive reduction potential. Hence, $F e^{3 +}$ is more stable than $M n^{3 +}$ but less stable than $C r^{3 +}$ .

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Similar questions

Q. For

M^{2 +} / M and M^{3 +} / M^{2 +}

systems,

E^{0}

values for some metals are as follows:

C r^{2 +} (a q) + 2 e^{-} \to C r (s); E^{0} = - 0.91 V C r^{3 +} (a q) + e^{-} \to C r^{2 +} (a q); E^{0} = - 0.41 V

M n^{2 +} (a q) + 2 e^{-} \to M n (s); E^{0} = - 1.2 V M n^{3 +} (a q) + e^{-} \to M n^{2 +} (a q); E^{0} = + 1.51 V

F e^{2 +} (a q) + 2 e^{-} \to F e (s); E^{0} = - 0.44 V F e^{3 +} (a q) + e^{-} \to F e^{2 +} (a q); E^{0} = + 0.77 V

Which of the following statement(s) is/are correct regarding the given standard reduction potentials?

Q. For

M^{2 +} / M

and

M^{3 +} / M^{2 +}

systems the

E^{⊖}

values for some metals are as follows:

$C r^{2 +} / C r$	$- 0.9 V$ $	$C r^{3} / C r^{2 +}$	$- 0.4 V$
$M n^{2 +} / M n$	$- 1.2 V$	$M n^{3 +} / M n^{2 +}$	$+ 1.5 V$
$F e^{2 +} / F e$	$- 0.4 V$	$F e^{3 +} / F e^{2 +}$	$+ 0.8 V$

Use this data to comment upon:
(i) the stability of

F e^{3 +}

in acid solution as compared to that of

C r^{3 +}

M n^{3 +}

and
(ii) the ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal

For M²⁺/M and M³⁺/M²⁺systems, the values for some metals are as follows:

Cr²⁺/Cr −0.9V

Cr³/Cr²⁺ −0.4 V

Mn²⁺/Mn −1.2V

Mn³⁺ /Mn²⁺ +1.5 V

Fe²⁺ /Fe −0.4V

Fe³⁺/Fe²⁺ +0.8 V

Use this data to comment upon:

(i) The stability of Fe³⁺ in acid solution as compared to that of Cr³⁺ or Mn³⁺and

(ii) The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.

For $\frac{M^{2 +}}{M}$ and $\frac{M^{3 +}}{M^{2 +}}$ systems the $E^{\circ}$ values for some metals are as follows:
$\frac{C r^{2 +}}{C r - 0.9 V}; \frac{C r^{3 +}}{C r^{2 +} - 0.4 V} \frac{M n^{2 +}}{M n - 1.2 V}; \frac{M n^{3 +}}{M n^{2 +}} + 1.5 V \frac{F e^{2 +}}{F e - 0.4 V}; \frac{F e^{3 +}}{F e^{2 +}} + 0.8 V$
Use this data to comment upon
(i) The stability of $F e^{3 +}$ in acid solution as compared to that of $C r^{3 +}$ or $M n^{3 +}$

The ease with which iron can be oxidised as compared to a similar process of either chromium or manganese metal.

Q. The correct order of

E^{0} M^{2 +} / M

values with negative sign for the four successive elements Cr, Mn, Fe and Co is

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$C r^{2 +} / C r$	$- 0.9 V$	$C r^{3 +} / C r^{2 +}$	$- 0.4 V$
$M n^{2 +} / M n$	$- 1.2 V$	$M n^{3 +} / M n^{2 +}$	$+ 1.5 V$
$F e^{2 +} / F e$	$- 0.4 V$	$F e^{3 +} / F e^{2 +}$	$+ 0.8 V$

For M2+/M and M3+/M2+ systems the E∘ values for some metals are as follows: Cr2+/Cr −0.9 V Cr3+/Cr2+ −0.4 V Mn2+/Mn −1.2 V Mn3+/Mn2+ +1.5 V Fe2+/Fe −0.4 V Fe3+/Fe2+ +0.8 V Choose the correct statements: