Which one of the following is used to identify glucose ?

Options

A. Neutral `FeCl_3`
B. `CHCl_3 + KOH ` (alc.)
C. `C_2 H_5 O Na`
D. Ammoniacal `AgNO_3`

Answer

To identify glucose, we can use Tollens' reagent, which is also known as ammonical silver nitrate (AgNO3). Here’s a step-by-step explanation of how this works:

### Step 1: Understand the Nature of Glucose
- Glucose is classified as a reducing sugar. This means it has the ability to donate electrons to other molecules, which is a key property that allows it to react with certain reagents.

**Hint:** Remember that reducing sugars can reduce metal ions to their elemental form.

### Step 2: Identify the Reagents
- The two common reagents used to identify reducing sugars are Tollens' reagent (ammonical AgNO3) and Fehling's solution. Both of these can be used to test for glucose.

**Hint:** Look for reagents that are known to react with reducing sugars.

### Step 3: Reaction with Tollens' Reagent
- When glucose is treated with Tollens' reagent, it reduces the silver ions (Ag+) present in the reagent to metallic silver (Ag), resulting in the formation of a shiny silver mirror on the surface of the test tube.

**Hint:** A visual change, such as a silver mirror, indicates a positive test for glucose.

### Step 4: Write the Chemical Reaction
- The reaction can be represented as follows:
\[ \text{Glucose} + 2 \text{Ag}^+ + 3 \text{OH}^- \rightarrow \text{Gluconate ion} + 2 \text{Ag} + 2 \text{H}_2\text{O} \]
- In this reaction, glucose is oxidized to gluconate ion, while silver ions are reduced to metallic silver.

**Hint:** Pay attention to the products formed in the reaction, as they can help confirm the presence of glucose.

### Step 5: Conclusion
- Therefore, the reagent used to identify glucose is ammonical AgNO3, which is Tollens' reagent.

**Final Answer:** Ammonical AgNO3 (Tollens' reagent) is used to identify glucose.