In which of the following reagent sodium potassium tartrate is used?

Question

Accepted Answer

Sodium potassium tartrate, also known as Rochelle salt, is specifically used in Fehling B solution. Here's a detailed explanation supporting why Option 4 is correct and why the other options are incorrect:

1. **Fehling B (Option 4):** Fehling's solution is used to test for the presence of reducing sugars. It consists of two separate solutions: Fehling A and Fehling B. Fehling A contains copper(II) sulfate, while Fehling B contains sodium potassium tartrate and sodium hydroxide. The sodium potassium tartrate acts as a complexing agent, stabilizing the copper(II) ions in solution. When mixed with Fehling A, it forms a deep blue solution that reacts with reducing sugars to form a red precipitate of copper(I) oxide. This is why sodium potassium tartrate is specifically associated with Fehling B.

2. **Tollen's reagent (Option 1):** Tollen's reagent is used to detect aldehydes and consists of a solution of silver nitrate in ammonia. It does not contain sodium potassium tartrate. Instead, it relies on the reduction of silver ions to metallic silver, which forms a mirror-like coating on the inside of the test tube.

3. **Bayer's reagent (Option 2):** Bayer's reagent is an alkaline solution of potassium permanganate used to test for unsaturation in organic compounds, such as alkenes and alkynes. It does not involve sodium potassium tartrate. The reagent works by oxidizing the unsaturated bonds, leading to a color change from purple to brown.

4. **Fehling A (Option 3):** Fehling A is the other component of Fehling's solution and contains copper(II) sulfate. It does not contain sodium potassium tartrate. The role of Fehling A is to provide the copper(II) ions that will react with the reducing sugars in the presence of Fehling B.

In summary, sodium potassium tartrate is specifically used in Fehling B solution as a complexing agent, which is why Option 4 is the correct answer. The other options do not involve sodium potassium tartrate in their composition or function.