Question

Nessler's reagent is prepared by mixing?

• A. Mercuric Chloride+ Sodium Hydroxide+ Potassium Iodide
• B. Potassium Chloride+ Sodium Hydroxide+ Mercuric Iodide
• C. Sodium Chloride+ Potassium Hydroxide+ Mercuric Iodide
• D. Mercuric Chloride+ Calcium Hydroxide+ Potassium Iodide

Hint:

Nessler's reagent is chemically \( \text{K}_2[\text{HgI}_4] \) in an alkaline medium. The mercury source is typically Mercuric Chloride (\( \text{HgCl}_2 \)), the iodide source is Potassium Iodide (KI), and the alkali is Sodium Hydroxide (\( \text{NaOH} \)).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Nessler's reagent is an alkaline chemical solution used primarily for the qualitative detection and quantitative estimation of ammonia or ammonium ions, which produces a yellow-to-brown coloration.

Step 2: Detailed Explanation:
- Nessler's reagent is chemically formulated as an alkaline solution of potassium tetraiodomercurate(II), represented as \( \text{K}_2[\text{HgI}_4] \).
- It is prepared by dissolving potassium iodide (KI) and mercuric chloride (\( \text{HgCl}_2 \)) in water, followed by the addition of a strong base, typically sodium hydroxide (\( \text{NaOH} \)) or potassium hydroxide (\( \text{KOH} \)).
- This specific reaction produces the active coordination complex required to detect nitrogenous adulterants (like urea or ammonium salts) in milk.

Step 3: Final Answer
The chemical constituents used to prepare Nessler's reagent are Mercuric Chloride, Sodium Hydroxide, and Potassium Iodide.