posted by Gary on .
what happens when HCl is added to CoCl2*6H20?
and what happens when you add AgNO3 to the product?
CoCl2*6H2O ==> Co(H2O)6^+2 + 2Cl^-
Co(H2O)6^+2 + 4Cl^- ==> CoCl4^-2 + 6H2O
Follow Le Chatelier's Principle. Most statements of this principle in texts are quite esoteric and they sound good. They are correct but students get confused with the wording. Here is a simplified statement: When a system is in equilibrium and we do something to it, the system tries to undo what we've done.
1. Adding HCl means we increase Cl-. The system will try to get rid of the extra Cl- we've added. How can it do that? Only one way. The reaction can shift to the right because that direction USES Cl- and that's what the reaction want to do.
2. If you add AgNO3, the Ag+ reacts with the Cl- for form AgCl(s), an insoluble ppt. So the Cl- is made smaller, the reaction now shifts to make the Cl- larger which means it shift to the left because that direction forms Cl-.