Consider the following reduction processes:
Zn2+ + 2e- - Zn(s); E° = -0.76 V
Ca2+ + 2e- - Ca(s); E

Q: Why does a negative reduction potential mean higher reducing power?

A negative reduction potential indicates that the substance prefers to lose electrons (oxidize) rather than gain them. Since reducing agents oxidize themselves to reduce others, a higher tendency to oxidize means a stronger reducing power.

Q: What is the difference between reducing power and oxidizing power?

Reducing power is the ability to reduce another substance (by losing electrons), while oxidizing power is the ability to oxidize another substance (by gaining electrons). They are inversely related.

Q: Can Calcium displace Zinc from a Zinc sulfate solution?

Yes. Since Calcium has a more negative reduction potential than Zinc, it is a stronger reducing agent and can displace Zinc from its salt solution.

Q: How do we remember the relationship between $E^\circ$ and reducing power?

Just remember: 'More negative $E^\circ$ = Wants to be oxidized = Stronger reducing agent'.

Q: Are these values measured against a standard?

Yes, all standard reduction potentials are measured relative to the Standard Hydrogen Electrode (SHE), which is assigned a potential of exactly $0.00\text{ V}$.

Question

Consider the following reduction processes:
$Zn^{2+} + 2e^- ightarrow Zn(s); E^\circ = -0.76	ext{ V}$
$Ca^{2+} + 2e^- ightarrow Ca(s); E^\circ = -2.87	ext{ V}$
$Mg^{2+} + 2e^- ightarrow Mg(s); E^\circ = -2.36	ext{ V}$
$Ni^{2+} + 2e^- ightarrow Ni(s); E^\circ = -0.25	ext{ V}$
The reducing power of the metals increases in the order

Options:

(A) $Zn < Mg < Ni < Ca$

(B) $Ni < Zn < Mg < Ca$

(C) $Ca < Zn < Mg < Ni$

(D) $Ca < Mg < Zn < Ni$

Sigma Percentile · Accepted Answer

### Decoding the Electrochemical Series
Have you ever wondered why some metals rust easily while others, like gold, stay shiny for centuries? It all comes down to their intrinsic desire to hold onto or give away their electrons. This problem is a beautiful illustration of that exact concept!

### The Meaning of Reduction Potential
We are given the standard reduction potentials for four metals: Nickel, Zinc, Magnesium, and Calcium. But what does this number actually tell us?

Think of the standard reduction potential as a measure of a metal's "hunger" for electrons. A positive value means the metal really wants to gain electrons and get reduced. Conversely, a negative value means the metal hates gaining electrons; it would much rather lose them and get oxidized!

### Connecting Potential to Reducing Power
Now, the question asks about **reducing power**. A reducing agent is a substance that reduces something else. To do that, it must give away its own electrons. Therefore, a strong reducing agent is simply a substance that loves to be oxidized.

If a metal loves to be oxidized, it must have a very low (highly negative) reduction potential. This gives us our golden rule: **The more negative the standard reduction potential, the stronger the reducing power.**

### Ranking the Metals
Let's look at our lineup:
Nickel has a potential of $-0.25	ext{ V}$.
Zinc sits at $-0.76	ext{ V}$.
Magnesium is at $-2.36	ext{ V}$.
Calcium is the most extreme at $-2.87	ext{ V}$.

Since Calcium has the most negative value, it is the most desperate to lose electrons. It is the strongest reducing agent in this group. Nickel, having the least negative value, is the weakest reducing agent.

Arranging them in increasing order of reducing power, we start with the weakest and end with the strongest:
$Ni < Zn < Mg < Ca$

And just like that, by understanding the physical meaning behind the numbers, the answer reveals itself perfectly!

Select Answer:

Visualized Solution

$E^{\circ} Values$

$Reducing Power Concept$

$Comparing E^{\circ} Values$

$Order of Reducing Power$

$Further Applications$

The Sigma Insight: Electrochemical Cells

Decoding the Electrochemical Series Have you ever wondered why some metals rust easily while others, like gold, stay shiny for centuries? It all comes down to their intrinsic desire to hold onto or give away their electrons

The Meaning of Reduction Potential We are given the standard reduction potentials for four metals

Connecting Potential to Reducing Power Now, the question asks about reducing power

Ranking the Metals Let's look at our lineup

Similar Questions

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Visualized Solution

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } E∘ Values

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } Reducing Power Concept

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } Comparing E∘ Values

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } Order of Reducing Power

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } Further Applications