Which of the following carbohydrates gives a dark blue colour with iodine?

Options

A. Amylopectin
B. Cellulose
C. Starch
D. none of these

Answer

To determine which carbohydrate gives a dark blue color with iodine, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks which carbohydrate reacts with iodine to produce a dark blue color.

2. **Identify the Carbohydrates**: The options provided are:
- A) Amylopectin
- B) Cellulose
- C) Starch
- D) None of these

3. **Recall the Reaction with Iodine**: It is known that certain carbohydrates, particularly starch, react with iodine to form a colored complex.

4. **Focus on Starch**: Starch is made up of two components: amylose and amylopectin. Amylose is a linear polymer, while amylopectin is branched. The iodine interacts specifically with the amylose component.

5. **Iodine-Starch Complex Formation**: When iodine (in the form of I5 ions) interacts with starch, it gets trapped in the helical structure of amylose. This interaction leads to the formation of a starch-iodine complex.

6. **Color Change**: The formation of this complex alters the energy levels of the electrons, allowing the complex to absorb visible light, which results in the intense blue color.

7. **Conclusion**: Based on the above information, the carbohydrate that gives a dark blue color with iodine is **C) Starch**.

### Final Answer:
The carbohydrate that gives a dark blue color with iodine is **C) Starch**.

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