已知下列物質(zhì)解離常數(shù)Kθa或Kθb值,欲配置PH=3的緩沖溶液,問(wèn)選擇哪種物質(zhì)是最合適? (1)HCOOH,Kθa=1.77×10-4 (2)HAc,Kθa=1.74×10-5 (3)NH3·H2O,Kθb=1.79×10-5