AL chemistry

chunhong, you're wrong.
silver ion does not necessarily preferentially react with chloride over chromate.
it all depends on concentration and their equilibrium constants.


圖片參考：http://imgcld.yimg.com/8/n/HA00075708/o/701107230100813873431871.jpg


2011-07-28 04:41:29 補充：
chunhong, it's YOU that should go back and study hard.
you've got some misconceptions on solubility products.

2011-07-30 02:17:03 補充：
not necessarily correct.
in addition to Ksp, initial concentrations of species also have to take into consideration.
as mentioned in my examples, even AgCl has lower solubility than Ag2CrO4, the later can be precipitated first;
even Ag2CrO4 has smaller Ksp in value, AgCl can precipitate first.

you should know that the mixture contains Cl-,K+ and CrO4 2- ions
when Ag+ is added to the mixture,Ag+first react with Cl- to form white ppt
When excess Ag+ is added to the mixture,since all the Cl- ions are reacted
the Ag+ would react with CrO4 2- and form Ag2CrO4 which is red solid.
Ag+ would prefer to react with Cl- first because AgCl is more stable compound compare to Ag2CrO4