Number of amphoteric compound among the following is `"______"`
(a) BeO
(b ) BaO
(c ) `Be(OH)_2`
(d ) `Sr(OH)_2`

Answer

To determine the number of amphoteric compounds among the given options, we need to analyze each compound based on the definition of amphoteric substances. Amphoteric compounds can act as both acids and bases.

### Step-by-Step Solution:

1. **Identify the Compounds**: The given compounds are:
- (a) BeO (Beryllium oxide)
- (b) BaO (Barium oxide)
- (c) Be(OH)₂ (Beryllium hydroxide)
- (d) Sr(OH)₂ (Strontium hydroxide)

2. **Analyze Each Compound**:
- **(a) BeO**: Beryllium oxide is amphoteric. It can react with acids to form beryllium salts and with bases to form beryllate ions.
- Reaction with acid: BeO + 2HCl → BeCl₂ + H₂O
- Reaction with base: BeO + 2NaOH + 2H₂O → Na₂Be(OH)₄

- **(b) BaO**: Barium oxide is basic. It does not exhibit amphoteric behavior as it primarily reacts with acids to form barium salts.
- Reaction with acid: BaO + 2HCl → BaCl₂ + H₂O
- It does not react with bases in a way that would indicate amphoteric behavior.

- **(c) Be(OH)₂**: Beryllium hydroxide is also amphoteric. It can react with both acids and bases.
- Reaction with acid: Be(OH)₂ + 2HCl → BeCl₂ + 2H₂O
- Reaction with base: Be(OH)₂ + 2NaOH → Na₂Be(OH)₄ + 2H₂O

- **(d) Sr(OH)₂**: Strontium hydroxide is basic. It does not exhibit amphoteric behavior as it primarily reacts with acids.
- Reaction with acid: Sr(OH)₂ + 2HCl → SrCl₂ + 2H₂O
- It does not react with bases in a way that would indicate amphoteric behavior.

3. **Count the Amphoteric Compounds**: From the analysis:
- Amphoteric: BeO, Be(OH)₂
- Not amphoteric: BaO, Sr(OH)₂

Therefore, there are **2 amphoteric compounds**.

### Final Answer:
The number of amphoteric compounds among the given options is **2**.

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