Why doesn't NaCl and HCl have the same effect on an equilibrium reaction

Question

Recently in my AP Chem class we did a simple reaction demonstrating equilibrium: [Co(H2O)6]2+(aq)(pink) + 4Cl-(aq) <--> [CoCl4]2-(aq)(blue) + 6H2O(l) (in an ethanol solution). The reaction demonstrates how when you add HCl the solution becomes more blue and water makes it pink. However we had a bit of a problem. Our lab also told us to add NaCl, saying that it would have a similar effect to HCl but "not the same". But for as much NaCl that we added we couldn't seem to see any change. My teacher doesn't know what's going so I was hoping you would. P.S I don't think it's an error with the lab like contaminated salt or solution because this lab was conducted 7 separate times with seperate people, plus my teacher says she's been doing it for years and has never figured out why it doesn't work.

Answer 1

The reason it doesn't work as well when adding NaCl is because its solubility in ethanol is not high to begin with.

 

If you calculate how much HCl you had to add in terms of stoichiometric equivalents in relation to CoCl2(aq) you would realize that the amount of NaCl needed in solution would never be reached and so, you would only slightly shift the equilibrium to the right.

 

I hope that clarified your question.