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 temperatue 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, the following steps occur:

### Step-by-Step Solution:

1. **Understanding the Reaction**: When an acid and a base are mixed, they undergo a chemical reaction known as a neutralization reaction. This process involves the acid neutralizing the basic properties of the base and vice versa.

2. **Identifying the Reactants**: For example, if we take hydrochloric acid (HCl) as the acid and sodium hydroxide (NaOH) as the base, we can analyze what happens when they are combined.

3. **Chemical Equation**: The neutralization reaction can be represented by the following chemical equation:
\[ \text{HCl (aq)} + \text{NaOH (aq)} \rightarrow \text{NaCl (aq)} + \text{H}_2\text{O (l)} \]
Here, sodium chloride (NaCl) is formed, which is commonly known as table salt, along with water.

4. **Exothermic Reaction**: The reaction between an acid and a base is typically exothermic. This means that it releases heat into the surroundings.

5. **Temperature Change**: Due to the exothermic nature of the reaction, the temperature of the solution increases. This is because the heat released during the reaction raises the temperature of the resulting solution.

6. **Final Observations**: Therefore, when an acid solution is mixed with a base solution, two main outcomes occur:
- The temperature of the solution increases.
- Salt formation takes place.

### Conclusion:
Based on the above analysis, the correct answers to the question are:
- (i) The temperature of the solution increases
- (iv) Salt formation takes place