Question

The question deals with the lab centering around chemical equilibria and Le Chatelier's principle using microscope techniques.

The main focus is on studying the equilibrium of the hexaaquacobalt(ll) complex ion.

1) Predict the direction in which the equilibrium should shift when you add ethyl alcohol to the mixture on Well C-2. Briefly Explain.

2) Briefly explain how your observations do or do not support your prediction.

The net ionic equation for the equilibrium involving the hexaaquacobalt(ll) ion in this experiment is:

CoCl4^2- + 6H2O<–> Co(H2O)6^2+ + 4CL-

I apologize for the inconvenience ahead of time. Thank you very much for your time and consideration. I will definitely give back great feedback to those who are willing to help me out. Thanks again.

Answer 1

The equilibrium reaction is given as

CoCl₄^2- (aq) + 6 H₂O (l) <=======> [Co(H₂O)₆]²⁺ (aq) + 4 Cl^- (aq)

The concentration equilibrium constant for the reaction is written as

K’ = [Co(H₂O)₆]²⁺[Cl^-]⁴/[CoCl₄^2-][H₂O]⁶

a) The addition of ethyl alcohol will shift the equilibrium to the left, i.e, the equilibrium will favor the reactants when ethyl alcohol is added to the equilibrium system.

b) Ethyl alcohol bonds to water, H₂O via hydrogen bonding and therefore, reduces the concentration of H₂O in the system. Consequently, [H₂O] falls and thus, the denominator tends to decrease in the expression above. However, K’ is a thermodynamic equilibrium constant and must remain unchanged at a particular temperature. To keep K’ constant, the numerator must decrease proportionately, i.e., the formation of [Co(H₂O)₆]²⁺ is suppressed and the reaction proceeds to the left, producing more H₂O.