答：
【1】已知 KCN 的pKa= 9.14 pKb= 4.86
【2】[OH-] = (cKb) ^1/2 = (10^-1 x 10^-4.86 )^1/2 = (10^-5.86 )^1/2 = 10^-2.93
【3】PH = 14 - POH = 14-2.93 = 11.07谢谢老师那就采纳吧