`5` mL of sodium sulphate solution is taken in a test tube and `5` mL of barium chloride solution is taken in another test tube. When the two solutions are mixed slowly and the test tube is left undisturbed for some time, a white precipitate is formed. Which of the following statements is correct about the above reaction ?

Options

A. It is a double displacement reaction since exchange of ions occurs between the two reactants.
B. It is a combination reaction since barium ions combine with sulphate ions to give barium sulphate
C. It is a displacement reaction since chloride ions are replaced by sulphate ions.
D. It is a neutralisation reaction since an acid reacts with alkali to give a salt.

Explanation

To solve the question regarding the reaction between sodium sulfate and barium chloride, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- We have sodium sulfate (Na2SO4) and barium chloride (BaCl2) as the reactants.

2. **Write the Chemical Equation**:
- When sodium sulfate and barium chloride are mixed, they undergo a double displacement reaction. The chemical equation for the reaction is:
\[ \text{Na}_2\text{SO}_4 + \text{BaCl}_2 \rightarrow \text{BaSO}_4 + 2\text{NaCl} \]

3. **Identify the Products**:
- The products of the reaction are barium sulfate (BaSO4), which is a white precipitate, and sodium chloride (NaCl).

4. **Observe the Formation of Precipitate**:
- When the two solutions are mixed, barium sulfate (BaSO4) forms as a white precipitate, indicating that a reaction has occurred.

5. **Determine the Type of Reaction**:
- This reaction is classified as a double displacement reaction (also known as a double replacement reaction) because the cations and anions of the reactants exchange partners.

6. **Evaluate the Options**:
- The question provides several statements about the reaction. Based on our analysis:
- **Option A**: It is a double displacement reaction. (Correct)
- **Option B**: It is a combination reaction. (Incorrect)
- **Option C**: It is a displacement reaction. (Incorrect)
- **Option D**: It is a neutralization reaction. (Incorrect)

7. **Conclusion**:
- The correct statement about the reaction is that it is a double displacement reaction.