Problem 59 - A Complete Resource Book in Chemistry for JEE Main

Question

\(\mathrm{Kl}\) and \(\mathrm{CuSO}_{4}\) solution when mixed gives (a) \(\mathrm{K}_{2} \mathrm{SO}_{4}+\mathrm{Cu}_{2} \mathrm{I}_{2}+\mathrm{I}_{2}\) (b) \(\mathrm{Cu}_{2} \mathrm{I}_{2}+\mathrm{K}_{2} \mathrm{SO}_{4}^{2}\) (c) \(\mathrm{CuI}_{2}+\mathrm{K}_{2} \mathrm{SO}_{4}\) (d) \(\mathrm{K}_{2} \mathrm{SO}_{4}+\mathrm{CuI}_{2}^{2}+\mathrm{I}_{2}\)

Step-by-Step Solution

Answer

Option (a) is correct: \(\mathrm{K}_{2} \mathrm{SO}_{4} + \mathrm{Cu}_{2} \mathrm{I}_{2} + \mathrm{I}_{2}\).

Step 1: Identify the Reactants

The reactants in the chemical reaction are potassium iodide (\(\mathrm{Kl}\)) and copper(II) sulfate (\(\mathrm{CuSO}_{4}\)).

Step 2: Analyze Possible Products

When \(\mathrm{Kl}\) and \(\mathrm{CuSO}_{4}\) are mixed, a double displacement reaction occurs. The possible products based on typical displacement reactions could be \(\mathrm{K}_{2}\mathrm{SO}_{4}\) and a compound involving copper and iodine.

Step 3: Recognize Redox Reaction

The presence of iodine and copper typically indicates a redox process, where \(\mathrm{Cu}^{2+}\) is reduced to \(\mathrm{Cu}_{2}\mathrm{I}_{2}\) and \(\mathrm{I}^{-}\) is oxidized to \(\mathrm{I}_{2}\).

Step 4: Write the Likely Products

Considering the redox outcomes and the typical double displacement products, the resultant compounds are \(\mathrm{K}_{2} \mathrm{SO}_{4}\), \(\mathrm{Cu}_{2} \mathrm{I}_{2}\), and \(\mathrm{I}_{2}\).

Step 5: Select the Correct Option

Comparing the calculated products with the options, choice (a) matches: \(\mathrm{K}_{2} \mathrm{SO}_{4} + \mathrm{Cu}_{2} \mathrm{I}_{2} + \mathrm{I}_{2}\).

Key Concepts

Redox Reaction

A redox reaction is a chemical process involving the transfer of electrons between two substances. In this type of reaction, one substance undergoes oxidation (loss of electrons), while the other undergoes reduction (gain of electrons). The term "redox" comes from two chemical processes which occur simultaneously: reduction and oxidation.

Oxidation involves an increase in oxidation state due to the loss of electrons. Conversely, reduction involves a decrease in oxidation state as a result of gaining electrons. It's important to understand that redox reactions drive many essential chemical processes, including those in our bodies and in various industrial applications.

In our specific case with potassium iodide and copper(II) sulfate, the iodine ion (\(I^{-}\)) is oxidized to molecular iodine (\(I_{2}\)), while the copper ion (\(Cu^{2+}\)) is reduced to cuprous iodide (\(Cu_{2}I_{2}\)). This exchange of electrons is crucial in forming the final products of the chemical equation.

Potassium Iodide

Potassium iodide (KI) is an ionic compound formed by the combination of potassium ions (\(K^{+}\)) and iodide ions (\(I^{-}\)). It is commonly used in medicine, photography, and as a nutritional supplement to provide iodine, essential for thyroid health. In chemistry, it plays a crucial role in various reactions, especially in redox processes.

When potassium iodide is involved in a reaction like the one with copper(II) sulfate, it acts as a source of iodide ions (\(I^{-}\)). These iodide ions participate actively in the redox reaction by being oxidized to iodine (\(I_{2}\)).

This transformation highlights the importance of potassium iodide not just as a nutrient, but as a reactive substance in chemical reactions, providing key reactants in the formation of desired products.

Copper(II) Sulfate

Copper(II) sulfate, often seen in its pentahydrate form as blue crystals, is a widely used chemical compound with the formula \(CuSO_4\). It encompasses a copper ion (\(Cu^{2+}\)) and a sulfate ion (\(SO_4^{2-}\)). Its applications range from agriculture to industry, where it's used in fungicides, herbicides, and analytical chemistry.

In the reaction with potassium iodide, copper(II) sulfate provides the copper ions necessary for the reaction. These copper ions (\(Cu^{2+}\)) are involved in the redox process, where they are reduced to the insoluble compound known as cuprous iodide (\(Cu_{2}I_{2}\)).

Copper(II) sulfate's role as a source of copper ions showcases its significance in many chemical reactions, especially where the transition of copper between oxidation states is needed to achieve the desired reaction outcome.