缓冲溶液.22.配制pH =7的缓冲溶液时,选择最合适的缓冲对是………………………( C )(Ka(HAc) = 1.8´10-5,Kb(NH3) = 1.8 ´10-5 ;H3PO4:Ka1 = 7.52´10-3,Ka2 = 6.23 ´10-8 ,Ka3 = 4.4x10-13;H2CO3:Ka1 = 4
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![缓冲溶液.22.配制pH =7的缓冲溶液时,选择最合适的缓冲对是………………………( C )(Ka(HAc) = 1.8´10-5,Kb(NH3) = 1.8 ´10-5 ;H3PO4:Ka1 = 7.52´10-3,Ka2 = 6.23 ´10-8 ,Ka3 = 4.4x10-13;H2CO3:Ka1 = 4](/uploads/image/z/4854921-33-1.jpg?t=%E7%BC%93%E5%86%B2%E6%BA%B6%E6%B6%B2.22.%E9%85%8D%E5%88%B6pH+%3D7%E7%9A%84%E7%BC%93%E5%86%B2%E6%BA%B6%E6%B6%B2%E6%97%B6%2C%E9%80%89%E6%8B%A9%E6%9C%80%E5%90%88%E9%80%82%E7%9A%84%E7%BC%93%E5%86%B2%E5%AF%B9%E6%98%AF%E2%80%A6%E2%80%A6%E2%80%A6%E2%80%A6%E2%80%A6%E2%80%A6%E2%80%A6%E2%80%A6%E2%80%A6%EF%BC%88+C+%EF%BC%89%28Ka%28HAc%29+%3D+1.8%26%23180%3B10-5%2CKb%28NH3%29+%3D+1.8+%26%23180%3B10-5+%EF%BC%9BH3PO4%EF%BC%9AKa1+%3D+7.52%26%23180%3B10-3%2CKa2+%3D+6.23+%26%23180%3B10-8+%2CKa3+%3D+4.4x10-13%EF%BC%9BH2CO3%EF%BC%9AKa1+%3D+4)
缓冲溶液.22.配制pH =7的缓冲溶液时,选择最合适的缓冲对是………………………( C )(Ka(HAc) = 1.8´10-5,Kb(NH3) = 1.8 ´10-5 ;H3PO4:Ka1 = 7.52´10-3,Ka2 = 6.23 ´10-8 ,Ka3 = 4.4x10-13;H2CO3:Ka1 = 4
缓冲溶液.
22.配制pH =7的缓冲溶液时,选择最合适的缓冲对是………………………( C )
(Ka(HAc) = 1.8´10-5,Kb(NH3) = 1.8 ´10-5 ;
H3PO4:Ka1 = 7.52´10-3,Ka2 = 6.23 ´10-8 ,Ka3 = 4.4x10-13;
H2CO3:Ka1 = 4.30´10-7,Ka2 = 5.61´10-11)
(A) HAc-NaAc (B) NH3-NH4Cl
(C) NaH2PO4-Na2HPO4 (D)NaHCO3-Na2CO3
缓冲溶液.22.配制pH =7的缓冲溶液时,选择最合适的缓冲对是………………………( C )(Ka(HAc) = 1.8´10-5,Kb(NH3) = 1.8 ´10-5 ;H3PO4:Ka1 = 7.52´10-3,Ka2 = 6.23 ´10-8 ,Ka3 = 4.4x10-13;H2CO3:Ka1 = 4
缓冲溶液的1:1浓度时 pH为 -logKa
如NH4+/NH3 是 -log(Kw/Kb)
HAc/NaAc 是 -logKa = -log1.8´10-5
具体等于几要用计算器算
缓冲溶液的 缓冲范围 pKa ±1,当pKa越接近pH,缓冲效果越好。
所以选 C。
NaH2PO4的pKa1 = H3PO4的pKa2 = 7.2,
最接近pH=7
配制pH =7的缓冲溶液时,选择最合适的缓冲对是………………………( C )
因为0.025mol/l NaH2PO4 -- 0.025mol/l Na2HPO4 的 pH值= 6.86 = 7