Question

Estimating the colored complex with chelating agent is _______________.

• A. Precipitometry
• B. Complexometry
• C. Argentometry
• D. Thiocyanometry

Hint:

Any titration that involves a "chelating agent" (like EDTA) to bind metal ions into stable ring structures is classified as a complexometric titration (Complexometry).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Volumetric analysis (titration) is classified into different categories based on the chemical reaction that occurs between the analyte and the titrant.
These include acid-base, redox, precipitation, and complex-forming titrations.

Step 3: Detailed Explanation:
Let us analyze the definition of the analytical methods listed in the options:
- Complexometry (Complexometric Titration): This method is based on the formation of a stable, soluble, and often colored coordination complex between metal ions (like $Ca^{2+}$ or $Mg^{2+}$) and a polydentate chelating agent (such as EDTA).
Metallochromic indicators (like Eriochrome Black T) are used to detect the endpoint by showing a distinct color change when the metal ions are fully chelated.
- Let us evaluate why the other options are incorrect:
- Precipitometry: Based on the formation of an insoluble precipitate during titration.
- Argentometry: A specific type of precipitation titration that uses silver nitrate ($\text{AgNO}_3$) as the titrant to determine halide ions.
- Thiocyanometry: Volumetric estimation using thiocyanate ions to determine silver or iron concentrations.
Therefore, estimating metal ions using a chelating agent to form a colored complex is termed Complexometry.

Step 4: Final Answer:
The method used to estimate a colored complex with a chelating agent is Complexometry.