3. To learn which metal hydroxides will form ammine complexes in NH 4. To be abl

ID: 1035070 • Letter: 3

Question

3. To learn which metal hydroxides will form ammine complexes in NH 4. To be able to calculate Kog for an overall reaction from K's for each step 5. To learn the defining equations for stability, formation and instability constants 6. To be able to write chemical equations demonstrating the acidic and the basic behavior of amphoteric hydroxides. In this experiment you will study the formation of two different types of complex ions, ammine complexes and hydroxo complexes. The distinction between amphoteric and non-amphoteric hydroxides will also be made. Procedure A. Place 3 mL of 0.10 N copper(II) sulfate solution in a test tube and add, drop by drop, 3.0 M ammonium hydroxide until a precipitate appears. 1. Write the balanced net ionic equation for the reaction which formed the precipitate and explain briefly how you determined the identity of the precipitate. 2. An equilibrium exists between a precipitate and its ions. Write the chemical equation for the equilibrium in this case. This equation is used to define the solubility product, Ksp, and the ion product, Q. Explain, in terms of Ksp and Q, why the precipitate formed. 3. Explain, in terms of Ksp and Q, what must happen to ion concentrations to cause this precipitate to dissolve.

Explanation / Answer

[1] chemical reaction between Copper (II) sulphate and ammonium hydroxide gives tetraaminecopper(II) sulphate, which is dark blue in color.

balanced chemical reaction is

CuSO4 + 4NH4OH -----> [Cu(NH3)4]SO4 + 4H2O

and, the balanced net ionic reaction is written by omitting the counter ion (here SO42-)

so, the net ionic reaction is

Cu2+ + 4NH4OH -----> [Cu(NH3)4]2+ + 4H2O

(dark blue)(this precipitates)

[2] Equilibrium exist between [Cu(NH3)4]2+ and Cu2+ ions. And, the equilibrium reaction is

[Cu(NH3)4]2+ <-----> Cu2+ + 4NH3

Solubility product (Ksp) is defined as the equilirium constant for the saturated solution and solid form (precipitate).

Ksp = [Cu2+] [NH3]4 , concentrations at equilibrium

For unsaturated and supersaturated solution, the system is not at equilibrium, in such case ion product (Q) is used which has same expression as Ksp.

Q = [Cu2+] [NH3]4

Precipitation occur when the concentration of species is higher than the equilirium value. According to Le Chatelier's principle, if the concentration of reactant is high, then equilibrium will favor the forward reaction (so that it diminishes the extra amount of reactant).

In terms of Ksp and Q, Precipitation will occur only when Q > Ksp or equal

[3] To dissove the precipitates Q should be less than Ksp (i.e., Q < Ksp )

As, Q = [Cu2+] [NH3]4 , Q can be brought down below Ksp by decreasing the concentration of ions. Removal of NH3 will also do the magic, and the same will be effect of addition of extra amount of water to the solution.

Navigate

3. To find a unit vector in the direction of the line that connects two points,

3. To prepare a buffer of pH 7.5 Given acid = HBrO conjugate base = BrO- pKa of

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.

3. To learn which metal hydroxides will form ammine complexes in NH 4. To be abl

Question

Explanation / Answer

Related Questions

Navigate