Understanding precipitation reactions


by ASidd
Tags: precipitate
ASidd
ASidd is offline
#1
Nov13-12, 03:52 AM
P: 73
"When the precipitating agent is added to the solution it causes it to become supersaturated. This starts the process of nucleation where ions and molecules will clump together to form small particles. A small amount of nucleation is necessary to start precipitation. However as the reaction progresses we need particle growth to occur rather than nucleation. Particle growth results in the formation of large 3 dimensional crystals. It is an opposite process to nucleation which favors supersaturated conditions. Thus to increase particle growth we must decrease supersaturation"

The above paragraph is what I wrote for an assignment. Can somebody guide me as to whether it is correct or incorrect?
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Amok
Amok is offline
#2
Nov13-12, 07:59 AM
P: 255
What exactly is you assignment? I honestly didn't understand why particle growth and nucleation are opposite processes and why it is that nucleation favors supersaturated conditions.
ASidd
ASidd is offline
#3
Nov14-12, 03:57 AM
P: 73
Quote Quote by Amok View Post
What exactly is you assignment? I honestly didn't understand why particle growth and nucleation are opposite processes and why it is that nucleation favors supersaturated conditions.

Nucleation is when initial atoms and ions join together to make small molecules. Then further atoms and molecules attach to these molecules and then even more so the particle size is larger. If there are many nucleation sites then there are too many molecules for the particles to attach to; so they are spread out and particles aren't as large.


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