Chemical Forums

Chemistry Forums for Students => High School Chemistry Forum => Topic started by: GregoryC4 on October 26, 2014, 02:45:38 PM

Title: Adding a compound to an equilibrium system?
Post by: GregoryC4 on October 26, 2014, 02:45:38 PM
Lets say you have a equilibrium system:

CoCl4-2 {blue} + 6 H2O   Co(H2O)6+2 {red} + 4 Cl- + heat

If you were to add KCl to the system, which side does the the compound add to? What is the chemical entity formed? Confused  ???

Thanks for your help everyone.
Title: Re: Adding a compound to an equilibrium system?
Post by: mjc123 on October 26, 2014, 03:18:37 PM
KCl will dissociate to K+ and Cl-. K+ doesn't react with anything in the system - it is a spectator ion. The Cl- will increase the concentration of Cl- already present. What effect will this have on the equilibrium?
Title: Re: Adding a compound to an equilibrium system?
Post by: GregoryC4 on October 26, 2014, 04:31:30 PM
Quote from: mjc123 on October 26, 2014, 03:18:37 PM
KCl will dissociate to K+ and Cl-. K+ doesn't react with anything in the system - it is a spectator ion. The Cl- will increase the concentration of Cl- already present. What effect will this have on the equilibrium?

Equilibrium will shift to the left to negate the increased concentration on the right? Thanks for your help, very simple and informative answer. 
Title: Re: Adding a compound to an equilibrium system?
Post by: GregoryC4 on October 26, 2014, 04:36:44 PM
If a compound where both the ions are "spectator ions", how would the equilibrium be affected? Would it even be affected at all?
My guess would be it just reduces the overall concentration at equilibrium.
Title: Re: Adding a compound to an equilibrium system?
Post by: mjc123 on October 27, 2014, 05:35:50 AM
If you just add a small amount of solid it won't significantly affect the concentrations. If you add it as solution, however, the concentrations will be reduced. If you add a significant amount of ions, you will change the ionic strength, and therefore the activity coefficients. Have you come across the concept of activity yet?