Sulphur trioxide is not directly dissolved in water to form sulphuric acid because

Options

A. 1. `SO_(3)` does not react with water to form acid
B. 2. `SO_(3)` gets oxidised to `H_(2)SO_(3)` when dissolved in water
C. 3. it results in the formation of dense fog of sulphuric acid which is difficult to condense
D. 4. sulphur trioxide is insoluble in water due to its covalent nature.

Answer

### Step-by-Step Solution:

1. **Understanding the Reaction**: Sulphur trioxide (SO₃) is a compound that can react with water (H₂O) to form sulphuric acid (H₂SO₄). The reaction can be represented as:
\[ SO_3 + H_2O \rightarrow H_2SO_4 \]

2. **The Contact Process**: In industrial settings, sulphuric acid is typically produced through the contact process, which involves the oxidation of sulphur dioxide (SO₂) to sulphur trioxide (SO₃) using oxygen and a catalyst (vanadium pentoxide, V₂O₅):
\[ 2SO_2 + O_2 \xrightarrow{V_2O_5} 2SO_3 \]

3. **Formation of Oleum**: Instead of directly dissolving SO₃ in water, it is first reacted with existing sulphuric acid to form oleum (H₂S₂O₇):
\[ SO_3 + H_2SO_4 \rightarrow H_2S_2O_7 \]

4. **Handling the Reaction with Water**: If SO₃ is added directly to water, it does not simply dissolve; instead, it reacts violently and produces a mist of sulphuric acid. This mist is a dense fog that is difficult to manage and can be hazardous.

5. **Conclusion**: Therefore, the reason sulphur trioxide is not directly dissolved in water to form sulphuric acid is that it results in the formation of a dense fog of sulphuric acid, which is difficult to condense and handle safely.

### Final Answer:
Sulphur trioxide is not directly dissolved in water to form sulphuric acid because it results in the formation of a dense fog of sulphuric acid, which is difficult to condense.

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