Question

欲使0.05mol固体Mg(OH)2刚好溶于0.5升NH4cl溶液中,则平衡时NH4cl的浓度为?

求详细解答

Answer 1

(1)Mg(OH)2 + 2NH4Cl <==> MgCI2 + 2NH.H2O
0.05mol--------0.1mol-------0.05mol----0.1mol
(2)Mg(OH)2 Ksp = 1.8*10^-11
[Mg2+]=0.05/0.5 =0.1mol/L [OH-] =1.34*10^-5
(3) NH3.H2O <==> NH4+ +OH-
Kb = [NH4+][ OH-]/[NH3.H2O]
[NH4+] = Kb[NH3.H2O]/[OH-]
=1.8*10^-5 *0.2/1.34*10^-5
= 0.28mol/L
(4)则平衡时NH4Cl的浓度0.28mol/L