Which of the following is incorrect?

Options

A. `FeCl_(3)` is used is detection of phenol
B. Fehling solution is used in detection of glucose
C. Tollen's reagent is used in detection of unsaturation
D. `NaHSO_(3)` is used in detection of carbonyl compound

Answer

To solve the question of which statement is incorrect, we will analyze each statement one by one.

### Step 1: Analyze Statement 1
**Statement:** FeCl3 is used in detection of phenol.

**Explanation:** This statement is true. When phenol is treated with FeCl3, it forms a violet-colored complex, indicating the presence of phenol. This is a well-known test for phenolic compounds.

### Step 2: Analyze Statement 2
**Statement:** Pellings solution is used in detection of glucose.

**Explanation:** This statement is also true. Pellings solution (similar to Tollens' reagent) can be used to detect aldehyde groups. Since glucose has an aldehyde group, it will react with Pellings solution, confirming the presence of glucose.

### Step 3: Analyze Statement 3
**Statement:** Tollens reagent is used in detection of unsaturation.

**Explanation:** This statement is incorrect. Tollens' reagent is specifically used to detect aldehydes, not unsaturation. It does not react with alkenes or alkynes to indicate unsaturation.

### Step 4: Analyze Statement 4
**Statement:** (Assuming a fourth statement exists for completion)

**Explanation:** Since we only analyzed three statements, we conclude that the third statement is the only incorrect one.

### Conclusion
The incorrect statement is:
**Tollens reagent is used in detection of unsaturation.**