I was out of town at the time, so I don’t know exactly how it _______.
A.
was happening
B.
happened
C.
happens
D.
has happened
手机使用
分享
复制链接
新浪微博
分享QQ
微信扫一扫
微信内点击右上角“…”即可分享
反馈
参考答案:
举一反三
【单选题】要配制 pH=4.0 的缓 冲溶液,应选用 ( ) A. NaH 2 PO 4 --Na 2 HPO 4 (p Ka =2.12,p Ka =7.20) B. HCOOH--HCOONa (p K =3.74) C. HAc--NaAc(p K =4.74) D. NaHCO 3 —Na 2 CO 3 (p Ka =6.38,p Ka =10.25)
A.
NaH 2 PO 4 --Na 2 HPO 4 (p Ka =2.12,p Ka =7.20) D. NaHCO 3 —Na 2 CO 3 (p Ka =6.38,p Ka =10.25)