第四章缓冲溶液

1、0.10 molL-1 NaCl溶液NaCl溶液中加入HCl到0.010 molL-1 ，溶液的pH由7变为2，改变了5个pH单位。0.10 molL-1 HAc 0.10 molL-1 NaAc溶液0.10 molL-1 HAc 0.10 molL-1 NaAc溶液溶液中加入HCl到0.010 molL-1 ，溶液的pH由4.75变为4.74，改变仅0.01pH单位。缓冲溶液的概念2.弱碱及其对应的盐：HCl = Cl- + H+平衡向逆方向移动H+增加当加入少量酸时，增多的H+与HCO3-生成H2CO3，使平衡向逆方向移动，溶液PH保持基本不变NaOH = Na+ + OH-H2O+平衡向

2、正方向移动当加入少量碱时，增多的OH-与H+生成H2O，使平衡向正方向移动，溶液PH保持基本不变OH-减少共轭酸共轭酸共轭碱共轭碱HAcNH4ClH2PO4-NaAcNH3H2OHPO42-抗抗酸酸成分成分缓冲系缓冲系抗抗碱碱成分成分组成示意图组成示意图质子转移平衡HAc+H2O Ac-+H3O+H2CO3+ H2O HCO3-+H3O+H3PO4+H2O H2PO4-+H3O+TrisH+H2O Tris+H3O+H2C8H4O4+H2O HC8H4O4-+H3O+NH4+H2O NH3+H3O+CH3NH3+H2O CH3NH2+H3O+H2PO4-+H2O HPO42-+H3O+HPO4

3、2-+H2O PO43-+H3O+缓冲系HAc-NaAcH2CO3-NaHCO3H3PO4-NaH2PO4TrisHCl -TrisH2C8H4O4- KHC8H4O4NH4Cl - NH3CH3NH3+Cl - CH3NH2NaH2PO4- Na2HPO4Na2HPO4- Na3PO4质子转移平衡HAc+H2O Ac-+H3O+H2CO3+ H2O HCO3-+H3O+H3PO4+H2O H2PO4-+H3O+TrisH+H2O Tris+H3O+H2C8H4O4+H2O HC8H4O4-+H3O+NH4+H2O NH3+H3O+CH3NH3+H2O CH3NH2+H3O+H2PO4-+H2

4、O HPO42-+H3O+HPO42-+H2O PO43-+H3O+缓冲系HAc-NaAcH2CO3-NaHCO3H3PO4-NaH2PO4TrisHCl -TrisH2C8H4O4- KHC8H4O4NH4Cl - NH3CH3NH3+Cl - CH3NH2NaH2PO4- Na2HPO4Na2HPO4- Na3PO4HBBlg p pH-a KHB + H2OH3O+ + B-HBBlg p pH HBBOH -a3aKK等等式式两两边边各各取取负负对对数数，HB B + H2OH3O+ + B-HBBlg p pH-a KHBBlg p pH-a KHB)()B(lg p pH-accK

5、HB)()B(lg p pH )(HB)/()()/B(lg p HB)()B(lg p pH-a-a-annKVnVnKccK溶液溶液HB)()B(lg p pH HB)(HB)()B()B(lg p HB)()B(lg p pH-a-a-aVVKVnVnKnnK7.21 1.0mmol1.0mmollg7.21 POHHPOlg p pH42-24a2K H3PO4 + NaOH Na2HPO4 + H2O反应前 200.10mmol 300.10mmol 反应后 1.0mmol 1.0mmol Na2HPO4 + NaOH NaH2PO4 + H2O反应前 2.0mmol 1.0mmol

6、 反应后 1.0mmol 1.0mmolHB)()B(lg p pH-accK cc/21/2pH pH pHpH dpH d)b(a)b(aVnVn越大，说明缓冲溶液的缓冲能力越强。越大，说明缓冲溶液的缓冲能力越强。 BHBBHBBBHBHB303. 2总c 576. 0BHB2121303. 2max BHBBHBBBHBHB303. 21ppH ppH 1-ppH :pH110 11 101 aaamax KKK缓冲比：减小减小11-1Lmol18. 0199Lmol20. 0)B()(HB)HB(L0.20molVVV11-1Lmol020. 0191Lmol20. 0)B()(HB)B(L0.20molVVV11111Lmol041. 0Lmol020. 0Lmol18. 0Lmol020. 0Lmol18. 0303. 2(HAc)(AclgppHaVVK240100lg.xxmL )100(mL lg76. 400. 5xx105144106 . 5108 . 1100 . 1)NH(aK141molg5 .53/ )ClNH(L35. 0Lmo