LeChâtelier\'s Principle: Buffers Date Lab Sec._ Name Desk No. A. Metal-Ammonia

Question

LeChâtelier's Principle: Buffers Date Lab Sec._ Name Desk No. A. Metal-Ammonia lons HCI Addition Color Account for the effects of NH,(a) and HC(ag) on the Cuso, or NiCl, solution. Use equations 16.2-5 in your explanation B. Multiple Equilibria with the Silver lon oObservation and net ionic equation for reaction. Use equation 156 to account for your observation Account for the observed chemical change from HNO, adition. Usc equations l67-8 to account for your observation. Thr ned clear OObservation from HCl addition and net ionic equation for the reaction. Use equation 16.9 to account for your observation. Thrned claudy Experiment 16 215 103

Explanation / Answer

Part A:

Effect of ammonia

NH3 + CuSO4 (light blue) [Cu(NH3)4(H2O)n]SO4 (dark blue)

   NH3 + NiCl2 (light green) [Ni(NH3)6]Cl2 (dark blue)

Excess ammonia willl shift the reaction equilibrium towards right hand side. Addition of HCl to the metal-ammonia complexes will shifth the equilibrium towards left hand side i.e metal salts willl form.

1. If we add NaOH instead of NH3, copper will precipitate as Cu(OH)2.

2NaOH + CuSO4 [Cu(OH)2] + Na2SO4

Part B: It is not clear from given details, what is the exact experiment is ?

Part C: The Bronsted acid equation is

CH3COOH + H2O CH3COO- + H3O+

Effect of NaCH3CO2:

Addition of NaCH3CO2 to equilibrium, will increase CH3COO- ions concentration. CH3COO- is a conjugate base of acetic acid. Note that the acid and conjugate base may react with one another, but when they do so, they simply trade places and the concentrations CH3COOH and CH3COO- do not change. So the pH of solution remains unchanged.

5(laboratory question):

If HCl is added to acetate buffer, the weak base ( CH3COO-) will react with the H+ from the HCl and form the CH3COOH. So, the H+ gets absorbed by the CH3COO- instead of reacting with water to form H3O+, so the pH change is very small.

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