Problem 105 - A Complete Resource Book in Chemistry for JEE Main

Question

The reaction potential values of \(\mathrm{M}, \mathrm{N}\) and \(\mathrm{O}\) are \(+2.46,-1.13\) and \(-3.13 \mathrm{~V}\) respectively. Which of the following order is correct, regarding their reducing property? (a) \(\mathrm{O}>\mathrm{N}>\mathrm{M}\) (b) \(\mathrm{O}>\mathrm{M}>\mathrm{N}\) (c) \(\mathrm{M}>\mathrm{N}>\mathrm{O}\) (d) \(\mathrm{M}>\mathrm{O}>\mathrm{N}\)

Step-by-Step Solution

Answer

(a) \(\text{O} > \text{N} > \text{M}\)

Step 1: Understand Reaction Potential

The reaction potential (also known as reduction potential) indicates an element's tendency to gain electrons and get reduced. Higher reduction potential means a greater tendency for reduction and thus a stronger reducing agent.

Step 2: Analyze Given Values

We have reaction potentials for three elements: \(\text{M} = +2.46\,\text{V}\), \(\text{N} = -1.13\,\text{V}\), and \(\text{O} = -3.13\,\text{V}\). To determine reducing strength, we typically consider the oxidation potentials. Strong reducing agents have lower (more positive when reversed to oxidation potential) reduction potentials.

Step 3: Arrange According to Reducing Property

Since lower or more negative reduction potentials (which translate to higher oxidation potentials, meaning stronger reduction capability when reversed) indicate stronger reducing properties, the order from strongest to weakest reducing agent is \(\text{O} > \text{N} > \text{M}\).

Step 4: Determine Correct Order

The correct order regarding the reducing properties based on the given reaction potentials, where lower reduction potential equals stronger reducing agent, is option (a): \(\text{O} > \text{N} > \text{M}\).

Key Concepts

Reduction Potential

In electrochemistry, the reduction potential is a crucial concept that tells us how likely an element or compound is to gain electrons and undergo reduction. This potential is usually measured in volts under standard conditions and is listed as a half-reaction in standard reduction tables.

• A positive reduction potential means the element or compound is more likely to gain electrons and be reduced.
• A negative reduction potential indicates a lower tendency to accept electrons.

By comparing the reduction potentials of different substances, we can predict which ones will be reduced and which will oxidize. In the given problem, the elements have reduction potentials of

• M: +2.46 V
• N: -1.13 V
• O: -3.13 V

The more positive the reduction potential, the better the substance is at being reduced, meaning it prefers to be on the gaining side of the electron exchange.

Oxidation Potential

While reduction potential focuses on gaining electrons, oxidation potential is essentially its opposite, concentrating on losing electrons. A substance's oxidation potential is obtained by taking the negative of its reduction potential.

• If an element has a higher oxidation potential, it is a better reducing agent.
• This is because it can lose electrons more readily.

In the exercise, substances with lower reduction potentials, like O with -3.13 V, actually have higher oxidation potentials. This suggests that O can easily lose electrons, making it a more potent reducing agent than M and N. The oxidation process can be understood as follows: - Substance A with a higher oxidation potential will donate electrons to Substance B with lower oxidation potential. - This process leads to Substance A being oxidized and Substance B being reduced. In electrochemical cell calculations, oxidation often occurs at the anode, while reduction takes place at the cathode, seamlessly completing the circuit.

Reducing Agent

A reducing agent, also known as a reductant, is an element or compound that donates electrons to another species, thereby reducing it.

• Itself gets oxidized in the process.
• It plays a fundamental role in redox reactions, which involve the transfer of electrons.

The strength of a reducing agent is inversely proportional to its reduction potential. Lower the reduction potential, the stronger the reducing agent because it gives up electrons more easily. In the example we have

• O with -3.13 V is the strongest reducing agent.
• N with -1.13 V follows next.
• M with +2.46 V is the weakest.

This order highlights the capability of each element to act as a reducing agent based on their willingness to lose electrons. An excellent real-world analogy would be how efficiently these substances can 'push' electrons onto others in electrochemical cells. This makes knowing the reducing property invaluable in predicting how substances will behave in chemical reactions.