Question

Elements trapped in between precipitate particles is _______

• A. Surface attraction
• B. Occlusion
• C. Precipitation
• D. Inclusion

Hint:

Remember: "Occlusion" means physical blockage or trapping. When crystals grow too fast, they "block" or trap foreign ions inside their lattice spaces. Slowing down precipitation (digestion) helps minimize occlusion.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
During gravimetric analysis, coprecipitation can cause soluble impurities to be carried down along with the desired precipitate.
Impurities can be incorporated into the precipitate particles through different physical or chemical mechanisms.

Step 2: Detailed Explanation:
Let us analyze the differences between the types of coprecipitation:
Occlusion (B): This occurs when a crystal grows rapidly during precipitation.
Impurities adsorbed on the surface of the rapidly growing crystal are covered and physically trapped within the interior of the growing crystal before they can dissolve or be replaced.
Therefore, elements trapped inside the precipitate particles represent occlusion.
Inclusion (D): This is a chemical substitution process where an impurity ion of similar size and charge replaces an analyte ion within the crystal lattice (forming a mixed crystal).
It is not a physical trapping process like occlusion.
Surface Attraction (A): This represents simple adsorption, where impurities are held weakly on the outer surface of the precipitate particles. They are not trapped inside.
Therefore, physical entrapment of elements inside the precipitate is called occlusion.

Step 3: Final Answer:
Elements trapped between precipitate particles represent Occlusion, which corresponds to option (B).