Problem 90 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following statements is incorrect? (a) lead is refined by electrolysis of PbSiF \(_{6}\). (b) red lead \(\left(\mathrm{Pb}_{3} \mathrm{O}_{4}\right)\) is known as minium (c) yellow lead oxide \((\mathrm{PbO})\) is known as massicot. (d) none of these

Step-by-Step Solution

Answer

The incorrect statement is (d) 'none of these'.

Step 1: Understanding Electrolysis of Lead

Let's analyze option (a). Lead is purified through the electrolysis of lead tetrafluorosilicate, or PbSiF (6). This is a correct statement because lead can be refined using this method.

Step 2: Identifying Red Lead

Consider option (b). Red lead or lead (II,IV) oxide has the chemical formula Pb (3) O (4) and is commonly known as minium. Therefore, this statement is correct.

Step 3: Identifying Yellow Lead Oxide

Review option (c). Yellow lead oxide, with the chemical formula PbO, is indeed known as massicot, meaning this statement is correct as well.

Step 4: Conclusion

Finally, evaluate option (d). Since all the previous statements (a, b, c) are correct, (d) 'none of these' being incorrect, must be the statement that is indeed incorrect.

Key Concepts

Lead Refinement

The process of lead refinement is an essential industrial activity that involves purifying crude lead to obtain the metal in a usable form. Electrolysis is a widely used method for refining lead. In electrolysis, a solution such as lead tetrafluorosilicate (PbSiF extsubscript{6}) serves as the electrolyte. Here’s a simplified overview of how this process works:

• The crude lead is submerged in the electrolyte solution.
• An electrical current is passed through, causing lead ions to migrate to the cathode (negative electrode).
• The ions then gain electrons and deposit as pure lead metal.

This electrochemical process is preferred because it allows for high-efficiency extraction of lead from its compounds. Electrolysis not only results in purer lead than some other methods but also is environmentally considerate, as it reduces impurities more effectively. Understanding the underlying chemistry is crucial for appreciating why electrolysis is favored in lead production.

Chemical Nomenclature

Chemical nomenclature is the system used to name chemical compounds in a way that conveys specific information about the structures and compositions of the substances. For example, the compound PbSiF extsubscript{6} is called lead tetrafluorosilicate, where:

• 'Pb' stands for lead.
• 'SiF extsubscript{6}' denotes the silicate group, with a fluorine component.

Proper chemical names help chemists communicate precisely and avoid confusion.
Red lead is another example, known chemically as lead (II,IV) oxide with the formula Pb extsubscript{3}O extsubscript{4}. The name minium is used for common reference, indicating historical or functional properties rather than the precise formula.
Similarly, PbO is called lead monoxide or commonly known as massicot in its yellow form. Knowing the names allows scientists to understand and predict the properties and behaviors of these compounds. Efforts in chemical nomenclature focus on providing clarity across various scientific fields.

Lead Oxides

Lead oxides are compounds made of lead and oxygen, with prominent ones being PbO and Pb extsubscript{3}O extsubscript{4}. Each variant has unique properties and uses.
Pbo - Lead Monoxide (Massicot)
PbO appears in two forms: massicot (yellow) and litharge (red). These are known as polymorphs — different crystal structures of the same compound. PbO is utilized widely in glass, ceramics, and batteries because of its stability and perfection as a precursor material.

• Massicot is the form where lead is of +2 oxidation state.
• The chemical formula is straightforward, indicating a basic lead oxide.

Pb extsubscript{3}O extsubscript{4} - Red Lead (Minium)
This variant has the chemical composition that signifies a mixed oxidation state of lead, (II) and (IV). Red lead is famous for its use as a pigment due to its bright hue and corrosion resistance in paints.

• Besides paints, it's a critical component in the manufacture of leaded glass.
• It’s also prevalent in automotive and battery industries.

Understanding lead oxides and their applications helps material scientists develop improved and innovative industrial materials.