When crystalizing a substance like aspirin, why does scratching on the flask speed this reaction up?
Answer:
the slowest part of the process of crystallization is the formation of the new phase. i.e. tiniest of crystals, which then start to grow at a much faster rate. by scratching the walls, you induce small scratches, or other irregularities on the surface, which help this initial crystal formation. another useful way to speed up crystallization is to add a few crystals of aspirin- the rest will crystallize around it.
Scratching of the sides of the flask causes some crystals of aspirin to fall off into the solution. These crystals act as seeds for crystallization to occur.
When a reaction is occurring in a super-saturated solution where crystallization is taking place, scratching a flask allows particles to move within the scratch allowing more room for an equilibrium to occur at standard conditions. :)
The answers post by the user, for information only, FunQA.com does not guarantee the right.
More Questions and Answers: