【正文】 用H2Bar 表示，p Ka1＝)。今稱取巴比妥 g，先加蒸餾水配成 100 mL 溶液，在 pH 計監(jiān)控下，加入 molL1NaOH 溶液 mL，并使溶液最后體積為 1000 mL。求此緩沖溶液的 pH 和緩沖容量。 （已知巴比妥的 Mr=184 gmol1）解 H 2Bar與NaOH的反應(yīng)為H2Bar(aq) + NaOH(aq)＝NaHBar(aq) +H 2O(l)反應(yīng)生成的NaHBar的物質(zhì)的量 n(NaHBar) ＝ c(NaOH)V(NaOH)＝ molL1 mL＝25 mmol，剩余H 2Bar的物質(zhì)的量為n余 (H2Bar)＝ n(H2Bar) n(NaOH)＝ 1000 25 mmol＝75 mmol1mol84.?gpH＝p Ka+lg ＝+lg ＝)(H2?75ol2 β ＝ ＝ molL 10L)5ol/17(l/??13. 分別加 NaOH 溶液或 HCl 溶液于檸檬酸氫鈉（縮寫 Na2HCit）溶液中。寫出可能配制的緩沖溶液的抗酸成分、抗堿成分和各緩沖系的理論有效緩沖范圍。如果上述三種溶液的物質(zhì)的量濃度相同，它們以何種體積比混合，才能使所配制的緩沖溶液有最大緩沖容量?（已知 H3Cit 的 pKa1=、p Ka2=、p Ka3=）`解.溶液組成 緩 沖 系抗酸成分抗堿成分有效緩沖范圍β 最大時體積比Na2HCit+HClH2CitHCit2HCit2 H2Cit ~ 2:1Na2HCit+HCl H3CitH2Cit H2Cit H3Cit ~ 2:3Na2HCit+NaOHHCit2Cit3 Cit3 HCit2 ~ 2:114. 現(xiàn)有 (1) molL1NaOH 溶液，(2) molL1NH3溶液，(3) molL1Na2HPO4 溶液各 50 mL，欲配制 pH= 的溶液，問需分別加入 molL1 HCl 溶液多少 mL？配成的三種溶液有無緩沖作用？哪一種緩沖能力最好？解 ⑴ HCl 與 NaOH 完全反應(yīng)需 HCl 溶液 50 mL。⑵ HCl(aq) + NH 3H2O(aq) = NH4Cl(aq) + H2O(l)NH4+的 pKa = = ， (Cl)(l).?????????解得 V(HCl) = 50 mL⑶ HCl(aq) + Na 2HPO4(aq) = NaH2PO4(aq) + NaCl(aq)H3PO4的 pKa2=， (HCl)(l).?????????解得 V (HCl) = 31 mL 第一種混合溶液無緩沖作用；第二種 pHpKa 1，無緩沖能力；第三種緩沖作用較強。15. 用固體 NH4Cl 和 NaOH 溶液來配制 1 L 總濃度為 molL1，pH= 的緩沖溶液，問需 NH4Cl 多少克？求需 molL1的 NaOH 溶液的體積（mL） 。解 設(shè)需 NH4Cl 的質(zhì)量為 xgpKa(NH4+) = = (NaOH)????????得 molL 1 V(NaOH) = [x/ gmol1 molL1 V(NaOH)]又 [ molL 1 VNaOH) + (x / mol1 molL1 V(NaOH))] / 1L= molL1解得 x = , V(NaOH) = L即：需 NH4Cl g，NaOH 溶液 L。16. 用 molL1H3PO4溶液和 molL1NaOH 溶液配制 100 mL pH= 的生理緩沖溶液，求需 H3PO4溶液和 NaOH 溶液的體積（mL） 。解 設(shè)第一步反應(yīng)需 H3PO4和 NaOH 溶液體積各為 x mL ⑴ H 3PO4(aq)+ NaOH(aq)= NaH2PO4(aq) + H2O(l)x mLH3PO4與 x mLNaOH 完全反應(yīng)，生成 NaH2PO4 molL1 x mL = x mmol⑵ 第二步反應(yīng)：設(shè)生成的 NaH2PO4再部分與 NaOH y mL 反應(yīng)，生成 Na2HPO4，其與剩余NaH2PO4組成緩沖溶液 NaH2PO4(aq) + NaOH(aq) = Na2HPO4(aq) + H2O(l)起始量 mmol + + 變化量 mmol + 平衡量 mmol (xy) 0 + mol)(.???=依題意又有 2 x + y = 100解得 x = ， y = 即需 H3PO4溶液 mL，NaOH 溶液( + ) mL = mL。17. 今欲配制 37℃時，近似 pH 為 的生理緩沖溶液，計算在 Tris 和 TrisHCl濃度均為 molL1的溶液 l00 mL 中，需加入 molL1HCl 溶液的體積（mL） 。在此溶液中需加入固體 NaCl 多少克，才能配成與血漿等滲的溶液？（已知 TrisHCl 在37℃時的 pKa＝，忽略離子強度的影響。 ） 解 ⑴ )HCl(. ) (Tris.40 1 Vn????????)l(?V(HCl) = mL⑵ 設(shè)加入 NaCl x g，血漿滲透濃度為 300 mmolL1= mol.)Tris(1????????c= molL1mHCl ??（ + 2）molL 1 + molL1?????x = ，即需加入 NaCl g18. 正常人體血漿中，[ ]＝ mmolL[CO 2(aq)]＝ mmolL1。若某?3HCO人因腹瀉使血漿中[ ]減少到為原來的 90%，試求此人血漿的 pH，并判斷是否會引起酸?3中毒。已知 H2CO3的 pKa1ˊ=。解 pH= p Ka1′ (aq)][COlg123 ????????pH 雖接近 ，但由于血液中還有其他緩沖系的協(xié)同作用，不會引起酸中毒。Exercises1. How do the acid and base ponents of a buffer function? Why are they typically a conjugate acidbase pair? Solution A buffer solution consists of a conjugate acidbase pair. The conjugate base can consume the added strong acid, and the conjugate acid can consume the added strong base, to maintain pH。The conjugate acidbase pairs of weak electrolytes present in the same solution at equilibrium.2. When H3O+ is added to a buffer，does the pH remain constant or does it change slightly？ Explain. Solution The pH of a buffer depends on the pKa of the conjugate acid and the buffer ponent ratio. When H3O+ is added to a buffer， the buffer ponent ratio changes slightly， so the pH changes slightly.3. A certain solution contains dissolved HCl and NaCl. Why can’t this solution act as a buffer?Solution This solution can’t act as a buffer. HCl is not present in solution in molecular form. Therefore, there is no reservoir of molecules that can react with added OH the Cl does not exhibit base behavior in water, so it cannot react with any H3O+ added to the solution.4. What is the relationship between buffer range and bufferponent ratio? Solution The pH of a buffer depends on the buffer ponent ratio. When [B]/[HB]=1, pH = pKa, the buffer is most effective. The further the bufferponent ratio is from 1，the less effective the buffering action is. Practically, if the [B]/[HB] ratio is greater than 10 or less than , the buffer is poor. The buffer has a effective range of pH = pKa177。1.5. Choose specific acidbase conjugate pairs of suitable for prepare the following beffers（Use Table 41 for Ka of acid or Kb of base）：（a）pH≈ ；（ b）pH≈；（c ）[H 3O+]≈109 molL1； Solution （a）HAc and Ac （b） and （c） and NH3?42PH?24?4NH6. Choose the factors that determine the capacity of a buffer from among the following and explain your choices.(a) Conjugate acidbase pair (b) pH of the buffer (c) Buffer ranger(d) Concentration of bufferponent reservoirs(e) Bufferponent ratio (f) pKa of the acid ponentSolution Choose (d) and (e). Buffer capacity depends on both the concentration of the reservoirs and the bufferponent ratio. The more concentrated the ponents of a buffer, the greater the buffer capacity. When the ponent ratio is close to one, a buffer is most effective.7. Would the pH increase or decrease, and would it do so to a larger or small extent, in each of the following cases:(a) Add 5 drops of molL1 NaOH to 100 mL of molL1 acetate buffer(b) Add 5 drops of molL1 HCl to 100 mL of molL1 acetate buffer(c) Add 5 drops of molL1 NaOH to 100 mL of molL1 HCl(d) Add 5 drops of molL1 NaOH to distilled waterSolution（a）The pH increases to a small extent。（b）The pH decreases to a small extent。（c）The pH increases to a small extent。（d）The pH increases to a larger extent.8. Which of the following solutions will show buffer properties?(a) 100 mL of molL1 NaC3H5O3 + 150 mL of molL1 HCl(b) 100 mL of molL1 NaC3H5O3 + 50 mL of molL1 HCl (c) 100 mL of molL1 NaC3H5O3+ 50 mL of molL1 NaOH (d) 100 mL of molL1 C3H5O3H + 50 mL of molL1 NaOH Solution (b) and (d)9. A chemist needs a pH buffe