Question

The standard electrode potentials of four metals \(\mathrm{A}, \mathrm{B}, \mathrm{C}\) and \(\mathrm{D}\) are given below. Based on these values, arrange them in the descending order of ease of deposition of metals from their salt solutions when subjected to electrolysis under standard conditions. (1) \(\rightarrow-0.9 \mathrm{~V}\) (2) \(\rightarrow-2.71 \mathrm{~V}\) (3) \(\rightarrow 0.77 \mathrm{~V}\) (4) \(\rightarrow 0.8 \mathrm{~V}\) (a) 4321 (b) 2134 (c) 3412 (d) 4312

Short answer

Question: Arrange the following metals in decreasing order of ease of deposition from their salt solutions when subjected to electrolysis under standard conditions: Metal A (-0.9 V), Metal B (-2.71 V), Metal C (0.77 V), Metal D (0.8 V). Answer: (b) 2134

Step-by-step solution

Listing the electrode potentials of the metals

List the given standard electrode potentials: Metal A: -0.9 V Metal B: -2.71 V Metal C: 0.77 V Metal D: 0.8 V

Arranging the electrode potentials in decreasing order

From the given standard electrode potentials values, we need to arrange the metals in the order of decreasing electrode potentials. The larger the negative value, the easier it is to deposit the metal from its salt solution: Metal B: -2.71 V Metal A: -0.9 V Metal C: 0.77 V Metal D: 0.8 V

Determine the answer using the arrangement from Step 2

Based on the arrangement of metals in Step 2, the answer corresponds to the order of metals in descending order of ease of deposition from their salt solutions: Metal B (2), Metal A (1), Metal C (3), and Metal D (4). Therefore, the correct answer is (b) 2134.

Key concepts

Standard Electrode Potentials

Standard electrode potentials are like a scoreboard for metals when they're part of electrochemical reactions. They are measured in volts and tell us how easily a metal can be reduced, or gain electrons, in a reaction.
These values are determined under standard conditions, which include a temperature of 25°C, a pressure of 1 atmosphere, and concentrations of solutions at 1 M.
The more positive a metal's electrode potential, the easier it is for that metal to attract electrons and be deposited from its solution during electrolysis. Conversely, a more negative value suggests that the metal does not easily gain electrons.

• Positive potentials: Easy reduction, preferred electron gain
• Negative potentials: Difficult reduction, not preferred for electron gain

By arranging metals based on their standard electrode potentials, we can predict which metal will deposit first during electrolysis. This is crucial in processes where the sequence of metal deposition is critical for manufacturing or refining operations.

Electrolysis

Electrolysis is like magic in chemistry, helping us extract or purify substances using electricity. It's often used to separate elements from their naturally occurring sources, like ores or salt solutions.
During electrolysis, an electric current is passed through a solution (or molten salt) causing chemical reactions at the electrodes and separating materials.
For metals in a solution, electrolysis involves:

• Anode: Positive electrode where oxidation occurs
• Cathode: Negative electrode where reduction occurs

When electrolysis is performed on a salt solution, metals tend to deposit at the cathode. The arrangement of metals based on standard electrode potentials tells us how easily each metal will deposit. This principle is the foundation of operations like electroplating and generating pure samples of metals for industrial use.

Metal Deposition

Metal deposition is the process by which metals are extracted from their ionic form in a solution and become solid at an electrode (typically the cathode) during electrolysis. The ease with which a metal deposits is directly related to its standard electrode potential.
Metals with more negative standard electrode potentials tend to deposit more readily, as they require less energy to gain electrons and form solid metal. This is pivotal in processes like metal refining and electroplating.
When metals deposit at the cathode:

• Their ions gain electrons (reduction) and become metal atoms.
• The solidity of the formed metal is based on the flow of electrons and their interaction with metal ions.

Understanding metal deposition helps us predict how metals behave in industrial applications, ensuring efficiency in processes from battery construction to decorative plating.

Salt Solutions

Salt solutions are primary players in the world of electrochemical reactions and electrolysis. These solutions contain dissolved ions, which can conduct electricity and participate in chemical transformations.
The ions in salt solutions come from compounds that dissociate, meaning they split into positive and negative ions.
These ions are critical during electrolysis:

• Positive ions (cations) move towards the cathode to gain electrons.
• Negative ions (anions) move towards the anode to lose electrons.

The efficiency and products of reactions in salt solutions depend on factors like concentration, temperature, and the nature of the dissolved salts. By understanding salt solutions, we can manipulate conditions to favor the desired chemical reactions, maximizing benefits in processes like electroplating and metal extraction.