What will happen if borontrifluoride is kept in moist air?

Options

A. it will strongly fume
B. It will partially hydrolyse.
C. It will completely hydrolyse
D. None of these

Explanation

To answer the question "What will happen if boron trifluoride is kept in moist air?", we can analyze the behavior of boron trifluoride (BF3) when it interacts with water vapor present in moist air.

### Step-by-Step Solution:

1. **Understanding Boron Trifluoride (BF3)**:
- Boron trifluoride is a colorless gas that is known to be a Lewis acid. It has a strong affinity for water and can react with it.

2. **Reaction with Moist Air**:
- When BF3 is exposed to moist air, it reacts with the water vapor present. The reaction can be represented as:
\[ BF3 + H2O \rightarrow H3O^+ + BF4^- \]
- This indicates that BF3 undergoes hydrolysis, where it reacts with water to form hydronium ions (H3O+) and tetrafluoroborate ions (BF4-).

3. **Formation of Dense White Fumes**:
- The reaction produces dense white fumes, which are typically due to the formation of boric acid (H3BO3) and other byproducts. The complete reaction can be complex, but it leads to the formation of products that can condense and create visible fumes.

4. **Partial Hydrolysis**:
- The hydrolysis of BF3 is often partial, meaning that not all BF3 molecules will react completely with water. Instead, a mixture of BF3, H3O+, and BF4- will exist in equilibrium.

5. **Conclusion**:
- Therefore, when boron trifluoride is kept in moist air, it will:
- Strongly fume due to the production of dense white fumes.
- Partially hydrolyze, leading to the formation of boric acid and other products.
- It does not completely hydrolyze, as some BF3 will remain unreacted.

### Final Answer:
When boron trifluoride is kept in moist air, it will strongly fume and partially hydrolyze.