Problem 84 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is a calomel? (a) \(\mathrm{HgBr}_{2}\) (b) \(\mathrm{Hg}_{2} \mathrm{Cl}_{2}\) (c) \(\mathrm{HgCl}\), (d) \(\mathrm{HgSO}_{4}\)

Step-by-Step Solution

Answer

The calomel is b Hg_{2}Cl_{2}, which is option (b).

Step 1: Understanding Calomel

Calomel is a mineral, scientifically known as mercurous chloride. Its chemical formula is \( \mathrm{Hg}_{2} \mathrm{Cl}_{2} \). This indicates that calomel is a compound made of mercury (Hg) and chlorine (Cl) in a specific ratio.

Step 2: Identify the Chemical Formula

Examine the given options to find the chemical formula of calomel. The options provided are: (a) \( \mathrm{HgBr}_{2} \) (b) \( \mathrm{Hg}_{2} \mathrm{Cl}_{2} \) (c) \( \mathrm{HgCl} \) (d) \( \mathrm{HgSO}_{4} \). The chemical formula for calomel, as identified in the previous step, is \( \mathrm{Hg}_{2} \mathrm{Cl}_{2} \).

Step 3: Match the Formula with Options

Compare the chemical formula \( \mathrm{Hg}_{2} \mathrm{Cl}_{2} \) with the options provided. Option (b) \( \mathrm{Hg}_{2} \mathrm{Cl}_{2} \) matches the chemical formula for calomel. Therefore, option (b) is the correct answer.

Key Concepts

Chemical Formulas

Chemical formulas are essential tools in chemistry, representing the elements present in a compound along with their respective proportions. They are like a recipe, offering precise information about the composition of molecules.

• For example, the chemical formula for water is \(\mathrm{H_{2}O}\). This shows that each water molecule is made up of two hydrogen atoms and one oxygen atom.
• Chemical formulas often use subscript numbers to indicate the quantity of each element.
• In our context, calomel is represented by \(\mathrm{Hg_{2}Cl_{2}}\), which reveals that it consists of two mercury atoms for every two chlorine atoms.

These formulas are important as they help chemists understand and predict the properties of substances.

Mercurous Chloride

Mercurous Chloride, also recognised as calomel, is an inorganic compound with the chemical formula \( \mathrm{Hg_{2}Cl_{2}} \). It is known for its historical use in medicine and chemistry.

• A significant property of mercurous chloride is its insolubility in water, making it stable under ordinary atmospheric conditions.
• It appears as a white or yellowish-white solid, often used in applications like reference electrodes in electrochemistry.
• Handling this compound requires care, as mercury and its compounds can be toxic.

The understanding of mercurous chloride helps in comprehending its applications and the safety measures required while working with it.

Inorganic Chemistry

Inorganic chemistry is a branch of chemistry that deals with inorganic compounds, mainly those that do not contain carbon-hydrogen bonds, which are typical in organic compounds.

• It encompasses a wide range of substances including metals, minerals, and organometallic compounds.
• This field is crucial for developing new materials and understanding natural processes like mineral formation.
• Examples of notable inorganic substances include salts, metals, and oxides, among which mercurous chloride is a classic example.

Inorganic chemistry supplies the theoretical and practical basis for working with compounds like calomel, helping chemists design and manipulate compounds in a controlled manner.