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Electrochemistry question

2022 · 27 Jun · Shift 2 · Q5

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2022 · 27 Jun · Shift 2 · Q5

Electrochemistry question

2022 · 27 Jun · Shift 2 · Q5

JEE MainChemistryElectrochemistryMCQ+4 / −1

In 3d series, the metal having the highest

M^{2+}

/M standard electrode potential is :

A
Cr
B
Fe
C
Cu
D
Zn

View written solutionFree

Correct answer: C

We need the metal with the highest standard electrode potential for the reduction:

$M^{2+} + 2e^- \rightarrow M$

A higher value of $E^\circ(M^{2+}/M)$ means the ion $M^{2+}$ is more easily reduced to the metal.

Let us compare the approximate standard electrode potentials of the given 3d-series metals:

For chromium: $E^\circ(\mathrm{Cr}^{2+}/\mathrm{Cr}) \approx -0.91\,\text{V}$
For iron: $E^\circ(\mathrm{Fe}^{2+}/\mathrm{Fe}) \approx -0.44\,\text{V}$
For zinc: $E^\circ(\mathrm{Zn}^{2+}/\mathrm{Zn}) = -0.76\,\text{V}$
For copper: $E^\circ(\mathrm{Cu}^{2+}/\mathrm{Cu}) = +0.34\,\text{V}$

Now compare these values:

$+0.34 > -0.44 > -0.76 > -0.91$

So the highest standard electrode potential is for copper.

Therefore, the correct option is:

$\boxed{\text{C: Cu}}$

Comparison with stored correct answer:

Stored correct answer = C

Our derived answer = C

Hence, they agree.

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