Can sodium carbonate extract be used test for `CO_(3)^(2-)` ions ?

Explanation

### Step-by-Step Solution:

1. **Understanding Sodium Carbonate Extract**: Sodium carbonate extract is prepared by mixing sodium carbonate (Na2CO3) with a sample that contains the ions to be tested. The extract itself contains carbonate ions (CO3^2-).

2. **Composition of Sodium Carbonate**: Sodium carbonate dissociates in solution to give sodium ions (Na^+) and carbonate ions (CO3^2-). Therefore, when we prepare the sodium carbonate extract, it inherently contains carbonate ions.

3. **Testing for Carbonate Ions**: To test for the presence of carbonate ions in a sample, we typically need a reagent that does not already contain the ions we are trying to detect. Since sodium carbonate extract contains carbonate ions, it cannot be used to test for the presence of additional carbonate ions in the sample.

...