Control test tube A contains 1 mL each of solutions of BiCl_3 and NH_3. Test tub
ID: 486955 • Letter: C
Question
Control test tube A contains 1 mL each of solutions of BiCl_3 and NH_3. Test tube B contains 1 mL each of solutions of BiCl_3, and NH_3 and 1 g of NH_4CI. A clear gelatinous precipitate of Bi(OH)_3 forms in test tube A while no precipitate forms in test tube B. the appearances of test tubes A and B are due to the interplay between the ammonia and bismuth hydroxide equilibria. What common ion is present in test tube B? How does the addition of this common ion affect the ammonia and bismuth hydroxide equilibria? Explain the results (differences in appearance between test tubes A and B) in terms of the common ion effect. What will happen in test tube A if conc. HCl is slowly added? Explain.Explanation / Answer
(a)
The common ion present in test tube B is NH4+
-------------------------------------------------------------
(b)
Common ion NH4+ restrics the formation of Bi(OH)3
-----------------------------------------------
(c)
NH3 in aqueous solution undergoes following equilibrium :
NH3 + H2O ==> NH4^+ + OH-
The OH_ generated in this step , then reacts with Bi^3+ to form a precipitate. If NH4 + ion is present in excces, the equilibrium will shoft to the left hand side and generation of OH- will be reduced. As a result there will be no precipitate formation.
--------------------------------------------
(d)
If HCl is added, it will provide excess Cl- in the solution. Like before, formation of Bi(OH)3 will be hindered in presence of this common ion.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.