Phenol is

Options

A. A base weaker than ammonia
B. An acid stronger than carbonic acid
C. An acid weaker that carbonic acid
D. A neutral compound

Answer

To determine the correct characterization of phenol from the given options, let's analyze each option step by step.

### Step 1: Understanding the Structure of Phenol
Phenol has the molecular formula C6H5OH. It consists of a hydroxyl group (-OH) attached to a benzene ring. This structure is crucial for understanding its acidic and basic properties.

**Hint:** Remember that the presence of the hydroxyl group in phenol is key to its acidic behavior.

### Step 2: Analyzing Option A - "A base weaker than ammonia"
Ammonia (NH3) is a well-known base due to its ability to donate a lone pair of electrons. In phenol, the lone pair of electrons on the oxygen atom is involved in resonance with the aromatic ring, making it less available for donation. Therefore, phenol is indeed a weaker base than ammonia.

**Hint:** Compare the availability of lone pairs in both compounds to assess their basicity.

### Step 3: Analyzing Option B - "An acid stronger than carbonic acid"
To evaluate this, we need to compare the acidity of phenol with carbonic acid (H2CO3). When phenol donates a proton, it forms the phenoxide ion (C6H5O-), which has several resonance structures that stabilize the negative charge. In contrast, carbonic acid, when it loses a proton, forms bicarbonate (HCO3-), which has fewer resonance structures. The stability of the conjugate base (phenoxide ion) indicates that phenol is a weaker acid than carbonic acid.

**Hint:** Consider the stability of the conjugate bases formed after deprotonation to determine acidity.

### Step 4: Analyzing Option C - "An acid weaker than carbonic acid"
From the previous analysis, we established that phenol is indeed a weaker acid than carbonic acid. Therefore, this statement is correct.

**Hint:** Look for the number of resonance structures in the conjugate bases to compare acidity.

### Step 5: Analyzing Option D - "A neutral compound"
Phenol is not neutral; it can act as an acid by donating a proton. Therefore, this statement is incorrect.

**Hint:** Recall that the ability to donate protons indicates that a compound is not neutral.

### Conclusion
Based on the analysis:
- Option A is correct: Phenol is a weaker base than ammonia.
- Option C is correct: Phenol is an acid weaker than carbonic acid.
- Options B and D are incorrect.

Thus, the correct answers are A and C.

### Final Answer
Phenol is:
- A. A base weaker than ammonia.
- C. An acid weaker than carbonic acid.