What happens when a solution of an acid is mixed with a solution of a base in a test tube ?
(i) The temperature of the solution increases
(ii) The temperature of the solution decreases
(iii) The temperature of the solution remains the same.
(iv) Salt formation takes place.

Options

A. Only (i)
B. (i) and (iii)
C. (ii) and (iii)
D. (i) and (iv)

Explanation

When a solution of an acid is mixed with a solution of a base in a test tube, several things happen. Let's analyze the process step by step:

### Step 1: Understanding the Reaction
When an acid (like hydrochloric acid, HCl) is mixed with a base (like sodium hydroxide, NaOH), they undergo a chemical reaction known as a neutralization reaction.

### Step 2: Formation of Salt and Water
The general equation for a neutralization reaction is:
\[ \text{Acid} + \text{Base} \rightarrow \text{Salt} + \text{Water} \]
For example:
\[ \text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O} \]
Here, sodium chloride (NaCl) is the salt formed, and water (H₂O) is also produced.

### Step 3: Energy Changes
Neutralization reactions are typically exothermic, meaning they release energy in the form of heat. As a result, the temperature of the solution increases when the acid and base are mixed.

### Step 4: Conclusion
Based on the above analysis, when an acid solution is mixed with a base solution:
1. The temperature of the solution increases (Option i).
2. Salt formation takes place (Option iv).

Therefore, the correct options are (i) and (iv).

### Final Answer
The correct answer is:
- (i) The temperature of the solution increases.
- (iv) Salt formation takes place.

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