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要配制 pH=4.0 的缓 冲溶液,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)
B.
HCOOH--HCOONa (p K =3.74)
D.
NaHCO 3 —Na 2 CO 3 (p Ka =6.38,p Ka =10.25)