If we use phenolphthalein as an indicator in a titration of `Na_(2)CO_(3)` with HCl, the usual result is

Options

A. No visible change is occur
B. The indicator reacts with the acid
C. The indicator reacts with the base
D. Sodium chloride and carbonic acid will be formed

Explanation

To solve the problem of what happens when phenolphthalein is used as an indicator in the titration of sodium carbonate (Na₂CO₃) with hydrochloric acid (HCl), we can follow these steps:

### Step 1: Understand the Reaction
When sodium carbonate reacts with hydrochloric acid, the following reaction occurs:

\[ \text{Na}_2\text{CO}_3 + 2 \text{HCl} \rightarrow 2 \text{NaCl} + \text{H}_2\text{O} + \text{CO}_2 \uparrow \]

This indicates that sodium carbonate (a basic salt) reacts with hydrochloric acid (a strong acid) to produce sodium chloride (a neutral salt), water, and carbon dioxide gas.

**Hint:** Identify the products of the reaction between Na₂CO₃ and HCl.

### Step 2: Identify the Role of Phenolphthalein
Phenolphthalein is a pH indicator that changes color depending on the pH of the solution. It is colorless in acidic solutions and turns pink in basic solutions.

**Hint:** Remember the color change of phenolphthalein at different pH levels.

### Step 3: Analyze the Titration Process
In this titration:
- Initially, the solution is basic due to the presence of Na₂CO₃.
- As HCl is added, the pH of the solution decreases.
- The endpoint of the titration occurs when all the Na₂CO₃ has reacted with HCl, and the solution becomes neutral or slightly acidic.

**Hint:** Consider what happens to the pH as you add HCl to the Na₂CO₃ solution.

### Step 4: Determine the Color Change at the Endpoint
At the endpoint of the titration, when all the carbonate has reacted, the solution will be neutral or slightly acidic. Since phenolphthalein is colorless in acidic solutions, the solution will remain colorless when the endpoint is reached.

**Hint:** Think about the color of phenolphthalein in acidic conditions.

### Conclusion
Therefore, the usual result when using phenolphthalein as an indicator in the titration of Na₂CO₃ with HCl is that the solution will change from pink (basic) to colorless (acidic) at the endpoint.

**Final Answer:** The solution will turn from pink to colorless at the endpoint of the titration.