Which of the following statements is not true regarding rayon?

Options

A. It is pure regenerated cellulose
B. It is obtained by dissolving wood pulp in alkaline `CS_2`
C. It is obtained by passing Na-salt of cellulose xanthate through spinneret into aqueous `NaHCO_3` solution
D. It is extracted as fibres of cellulose

Answer

To determine which statement regarding rayon is not true, let's analyze each statement step by step.

### Step 1: Evaluate the first statement
**Statement:** "It is pure regenerated cellulose."
- **Analysis:** Rayon is indeed made from cellulose, which is derived from wood pulp. The process of making rayon involves regenerating cellulose from its soluble form. Therefore, this statement is true.

### Step 2: Evaluate the second statement
**Statement:** "It is obtained by dissolving wood pulp in alkaline CS2."
- **Analysis:** This statement is incorrect. When wood pulp is dissolved in alkaline CS2, it results in the formation of cellulose xanthate, not rayon. Rayon is produced from the sodium salt of cellulose xanthate, not directly from dissolving wood pulp in alkaline CS2. Thus, this statement is not true.

### Step 3: Evaluate the third statement
**Statement:** "It is obtained by passing Na salt of cellulose xanthate through spinneret into aqueous NaHCO3 solution."
- **Analysis:** This statement is true. The production of rayon involves extruding the sodium salt of cellulose xanthate through a spinneret into a solution, typically sodium bicarbonate (NaHCO3), which regenerates the cellulose and forms rayon fibers.

### Step 4: Evaluate the fourth statement
**Statement:** "It is extracted as fibres of cellulose."
- **Analysis:** This statement is also true. Rayon is indeed extracted as fibers that are regenerated cellulose, confirming that it is a cellulose-based fiber.

### Conclusion
After evaluating all the statements:
- The first, third, and fourth statements are true.
- The second statement is not true.

### Final Answer
The statement that is not true regarding rayon is: **"It is obtained by dissolving wood pulp in alkaline CS2."**

---