Question

Zn(s) is used to reduce other compounds in chemical reactions. If a chemist needs a substance that is more effective in its reducing ability, which of the following species would be the best choice?
A) Na
B) H+
C) K+
D) Cl−

Answer 1

Answer: Sodium element has the highest reducing ability.

Explanation:

Reducing ability of an element is defined as the ability for an element to loose electrons. It helps the other element to gain electrons and thus act as reducing agent.

Reducing agent undergoes oxidation reaction.

The substance having highest positive $E^o$ reduction potential will always get reduced and will undergo reduction reaction. Or, the substance having highest negative $E^o$ reduction potential will always get oxidized and will undergo oxidation reaction.

For the given options:

Option A: Sodium

The standard reduction potential of this element will be:

$Na\rightarrow Na^++e^-;E^o_{Na^+/Na}=-2.71V$

Option B: Hydrogen ion

This element cannot loose further electrons. So, now it will gain electrons.

The standard reduction potential of this element will be:

$2H^++2e^-\rightarrow H_2;E^o_{H^+/H_2}=0V$

Option C: Potassium ion

This element cannot loose further electrons. So, now it will gain electrons.

The standard reduction potential of this element will be:

$K^++e^-\rightarrow K;E^o_{K^+/K}=2.93V$

Option D: Chlorine ion

The standard reduction potential of this element will be:

$Cl_2+2e^-\rightarrow 2Cl^-;E^o_{Cl_2/Cl^-}=1.36V$

As, the standard reduction potential of sodium element is more negative, it will act as reducing agent.

Hence, sodium element has the highest reducing ability.