2. Acid-Base Titrations

3. TITRATIONS

4. TITRATIONS Purpose: To determine the unknown concentration of the acid.

5. Titration Curve TITRATIONS

6. Indicator Ranges TITRATIONS

7. Indicator Ranges TITRATIONS

12. STRONG-WEAK TITRATIONS

13. Strong-Weak Titration Curves STRONG-WEAK TITRATIONS

16. Buffers STRONG-WEAK TITRATIONS

21. Calculations In a titration, 20.0 mL of 0.300 M HCl(aq) is titrated with 0.300 M NaOH(aq). What is the pH of the solution after the following volumes of NaOH(aq) have been added? a) 0.00 mL b) 10.0 mL c) 20.0 mL d) 30.0 mL NaOH (aq) + HCl (aq)  NaCl (aq) + H 2 O (l) a) pH = -log [H + ] pH = -log [0.300] pH = 0.5 b) n HCl =0.006mol n NaOH =CV n NaOH =(0.300M)(0.010L) n NaOH =0.003 mol n HCl leftover =0.006mol-0.003mol n HCl leftover =0.003mol pH = -log [H + ] pH = -log [0.1] pH = 1.00 C=n/V total C=0.003mol/0.030L C=0.1M TITRATIONS

22. Calculations In a titration, 20.0 mL of 0.300 M HCl(aq) is titrated with 0.300 M NaOH(aq). What is the pH of the solution after the following volumes of NaOH(aq) have been added? a) 0.00 mL b) 10.0 mL c) 20.0 mL d) 30.0 mL NaOH (aq) + HCl (aq)  NaCl (aq) + H 2 O (l) c) n HCl =0.006mol n NaOH =CV n NaOH =(0.300M)(0.020L) n NaOH =0.006 mol n HCl leftover =0mol pH = -log [H + ] pH = -log [1.0x10 -7 ] pH = 7 d) n HCl =0.006mol n NaOH =CV n NaOH =(0.300M)(0.030L) n NaOH =0.009 mol n NaOH leftover =0.009mol-0.006mol n NaOH leftover =0.003mol C=n/V total C=0.003mol/0.050L C=0.06M TITRATIONS

23. Calculations In a titration, 20.0 mL of 0.300 M HCl(aq) is titrated with 0.300 M NaOH(aq). What is the pH of the solution after the following volumes of NaOH(aq) have been added? a) 0.00 mL b) 10.0 mL c) 20.0 mL d) 30.0 mL NaOH (aq) + HCl (aq)  NaCl (aq) + H 2 O (l) d) pOH = -log [OH - ] pOH = -log [0.06] pOH = 1.22 pH = 12.8 TITRATIONS

24. Calculations In a titration 20.0 mL of 0.300 M HC 2 H 3 O 2(aq) with 0.3 M NaOH (aq) , what is the pH of the solution after the following volumes of NaOH (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL HC 2 H 3 O 2(aq) <===> H + (aq) + C 2 H 3 O 2 - (aq) a) I 0.300M 0 0 C -x +x +x E 0.300-x x x K a = [H + (aq) ][C 2 H 3 O 2 - (aq) ] [HC 2 H 3 O 2(aq) ] 1.8x10 -5 = [x][x] [0.300-x]  Assumption used 2.32379x10 -3 = x pH = -log [H + ] pH = -log [2.32x10 -3 ] pH = 2.63 .: pH = 2.63 STRONG-WEAK TITRATIONS

25. Calculations In a titration 20.0 mL of 0.300 M HC 2 H 3 O 2(aq) with 0.3 M NaOH (aq) , what is the pH of the solution after the following volumes of NaOH (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL HC 2 H 3 O 2(aq) <===> H + (aq) + C 2 H 3 O 2 - (aq) b) NaOH  Na + (aq) + OH - (aq) V total =0.030L n NaOH =CV n NaOH =(0.3M)(0.010L) n NaOH = 0.003 mol  so 0.003 mol of HC 2 H 3 O 2 are used  so 0.003 mol of C 2 H 3 O 2 - are formed n HC 2 H 3 O 2 =(0.300M)(0.020L) n HC 2 H 3 O 2 =0.006mol  so 0.003 mol of HC 2 H 3 O 2 remain C=n/V total C=0.003mol/0.030L C=0.1M STRONG-WEAK TITRATIONS

26. Calculations In a titration 20.0 mL of 0.300 M HC 2 H 3 O 2(aq) with 0.3 M NaOH (aq) , what is the pH of the solution after the following volumes of NaOH (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL HC 2 H 3 O 2(aq) <===> H + (aq) + C 2 H 3 O 2 - (aq) C=0.1M I 0.1 0 0.1 C -x +x +x E 0.1-x x 0.1+x 1.8x10 -5 = [x][0.1+x] [0.1-x]  Assumption used 1.8x10 -5 = [x][0.1] [0.1] 1.8x10 -5 = x pH = -log [H + ] pH = -log [1.8x10 -5 ] pH = 4.74 .: pH = 4.74 b) STRONG-WEAK TITRATIONS

27. Calculations In a titration 20.0 mL of 0.300 M HC 2 H 3 O 2(aq) with 0.3 M NaOH (aq) , what is the pH of the solution after the following volumes of NaOH (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL HC 2 H 3 O 2(aq) <===> H + (aq) + C 2 H 3 O 2 - (aq) c) NaOH  Na + (aq) + OH - (aq) At equivalence point, the #mol acid = #mol base n HC 2 H 3 O 2 =(0.300M)(0.020L) = 0.006mol = n NaOH V= n NaOH C V= 0.006mol 0.3M V=0.02L  V total =0.040L Since n acid =n conjugate base , 0.006mol of C 2 H 3 O 2 - were formed STRONG-WEAK TITRATIONS

28. Calculations In a titration 20.0 mL of 0.300 M HC 2 H 3 O 2(aq) with 0.3 M NaOH (aq) , what is the pH of the solution after the following volumes of NaOH (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL C 2 H 3 O 2 - (aq) + H 2 O (l) <===> OH - (aq) + HC 2 H 3 O 2(aq) c)  V total =0.040L I 0.15 0 0 C -x +x +x E 0.15-x x x  C= n V C= 0.006mol 0.040L C=0.15M K b = [OH - (aq) ][HC 2 H 3 O 2(aq) ] [C 2 H 3 O 2 - (aq) ] K b = [x][x] [0.15-x] What is the K b value? STRONG-WEAK TITRATIONS

29. Calculations In a titration 20.0 mL of 0.300 M HC 2 H 3 O 2(aq) with 0.3 M NaOH (aq) , what is the pH of the solution after the following volumes of NaOH (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL C 2 H 3 O 2 - (aq) + H 2 O (l) <===> OH - (aq) + HC 2 H 3 O 2(aq) c) I 0.15 0 0 C -x +x +x E 0.15-x x x 5.555556x10 -10 = [x][x] [0.15-x] K a x K b = K w K b = K w K a K b = 1.0x10 -14 1.8x10 -5 K b = 5.555556x10 -10  Assumption used 5.555556x10 -10 = [x][x] [0.15] 9.128709x10 -6 = x 9.1287x10 -6 9.1287x10 -6 0.15 STRONG-WEAK TITRATIONS

30. Calculations In a titration 20.0 mL of 0.300 M HC 2 H 3 O 2(aq) with 0.3 M NaOH (aq) , what is the pH of the solution after the following volumes of NaOH (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL C 2 H 3 O 2 - (aq) + H 2 O (l) <===> OH - (aq) + HC 2 H 3 O 2(aq) c) I 0.15 0 0 C -x +x +x E 0.15-x x x 9.1287x10 -6 9.1287x10 -6 0.15 pOH = -log [OH - ] pOH = -log [9.128709x10 -6 ] pOH = 5.03959 pH = 14-5.03959 pH = 8.96 .: pH = 8.96 STRONG-WEAK TITRATIONS

31. Calculations In a titration 20.0 mL of 0.300 M HC 2 H 3 O 2(aq) with 0.3 M NaOH (aq) , what is the pH of the solution after the following volumes of NaOH (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL C 2 H 3 O 2 - (aq) + H 2 O (l) <===> OH - (aq) + HC 2 H 3 O 2(aq) d) n NaOH =CV n NaOH =(0.3M)(0.030L) n NaOH =0.009mol n HC 2 H 3 O 2 =(0.300M)(0.020L) = 0.006mol  0.003mol of NaOH will remain after equivalence point has been reached STRONG-WEAK TITRATIONS

32. Calculations In a titration 20.0 mL of 0.300 M HC 2 H 3 O 2(aq) with 0.3 M NaOH (aq) , what is the pH of the solution after the following volumes of NaOH (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL C 2 H 3 O 2 - (aq) + H 2 O (l) <===> OH - (aq) + HC 2 H 3 O 2(aq) d) n NaOH remaining = 0.003mol  V total =0.050L  C = n NaOH V C = 0.003mol 0.050L C = 0.06M n C 2 H 3 O 2 - = 0.006mol C = n C 2 H 3 O 2 - V C = 0.006mol 0.050L C = 0.12M STRONG-WEAK TITRATIONS

33. Calculations In a titration 20.0 mL of 0.300 M HC 2 H 3 O 2(aq) with 0.3 M NaOH (aq) , what is the pH of the solution after the following volumes of NaOH (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL C 2 H 3 O 2 - (aq) + H 2 O (l) <===> OH - (aq) + HC 2 H 3 O 2(aq) d) I 0.12 0.06 0 C -x +x +x E 0.12-x 0.06+x x K b = 5.555556x10 -10 = [0.06+x][x] [0.12-x]  Assumption used 5.555556x10 -10 = [0.06][x] [0.12] 1.1111x10 -9 = x 1.1111x10 -9 0.06 0.12 STRONG-WEAK TITRATIONS

34. Calculations In a titration 20.0 mL of 0.300 M HC 2 H 3 O 2(aq) with 0.3 M NaOH (aq) , what is the pH of the solution after the following volumes of NaOH (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL C 2 H 3 O 2 - (aq) + H 2 O (l) <===> OH - (aq) + HC 2 H 3 O 2(aq) d) I 0.12 0.06 0 C -x +x +x E 0.12-x 0.06+x x 1.1111x10 -9 0.06 0.12 pOH = -log [OH - ] pOH = -log [0.06] pOH = 1.2218 pH = 14-1.2218 pH = 12.78 .: pH = 12.8 STRONG-WEAK TITRATIONS

35. Calculations In a titration 20.0 mL of 0.1 M NH 3(aq) is titrated with 0.1 M HCl (aq) . What is the pH of the resulting solution after the following volumes of HCl (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL NH 3(aq) + H 2 O (l) <===> OH - (aq) + NH 4 + (aq) a) I 0.1M 0 0 C -x +x +x E 0.1-x x x K b = [OH - (aq) ][NH 4 + (aq) ] [NH 3(aq) ] 1.8x10 -5 = [x][x] [0.1-x]  Use assumption 1.34164x10 -3 = x pOH = -log [OH - ] pOH = -log [1.34x10 -3 ] pOH = 2.87 pH = 14 - 2.87 pH = 11.13 .: pH = 11.13 STRONG-WEAK TITRATIONS

36. Calculations In a titration 20.0 mL of 0.1 M NH 3(aq) is titrated with 0.1 M HCl (aq) . What is the pH of the resulting solution after the following volumes of HCl (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL NH 3(aq) + H 2 O (l) <===> OH - (aq) + NH 4 + (aq) b) n NH 3 =CV n NH 3 =(0.1M)(0.020L) n NH 3 =0.002 mol n HCl =CV n HCl =(0.1M)(0.010L) HCl (aq)  H + (aq) + OH - (aq) n HCl =0.001mol n NH 4 + formed =0.001 mol n NH 3 remaining =0.001 mol V total =0.030L C=n/V total C=0.001mol/0.030L C=0.0333M STRONG-WEAK TITRATIONS

37. Calculations In a titration 20.0 mL of 0.1 M NH 3(aq) is titrated with 0.1 M HCl (aq) . What is the pH of the resulting solution after the following volumes of HCl (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL NH 3(aq) + H 2 O (l) <===> OH - (aq) + NH 4 + (aq) b) I 0.0333 0 0.0333 C -x +x +x E 0.0333-x x 0.0333+x 1.8x10 -5 = [x][0.0333+x] [0.0333-x]  Use assumption 1.8x10 -5 = [x][0.0333] [0.0333] 1.8x10 -5 = x pOH = -log [OH - ] pOH = -log [1.8x10 -5 ] pOH = 4.74 .: pH = 9.26 pH = 14 - 4.74 pH = 9.26 STRONG-WEAK TITRATIONS

38. Calculations In a titration 20.0 mL of 0.1 M NH 3(aq) is titrated with 0.1 M HCl (aq) . What is the pH of the resulting solution after the following volumes of HCl (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL NH 3(aq) + H 2 O (l) <===> OH - (aq) + NH 4 + (aq) c) HCl (aq)  H + (aq) + OH - (aq) n NH 3 =CV n NH 3 =(0.1M)(0.020L) n NH 3 =0.002 mol = n HCl at equivalence point = n NH 4 + at equivalence point V= n HCl C V= 0.002mol 0.1M V=0.02L  V total =0.040L C= n NH 4 + V C= 0.002mol 0.040L C=0.05mol/L STRONG-WEAK TITRATIONS

39. Calculations In a titration 20.0 mL of 0.1 M NH 3(aq) is titrated with 0.1 M HCl (aq) . What is the pH of the resulting solution after the following volumes of HCl (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL NH 4 + (aq) <===> NH 3(aq) + H + (aq) I 0.05 0 0 C -x +x +x E 0.05-x x x 5.555x10 -10 = [x][x] [0.05-x]  Use assumption 5.555x10 -5 = [x][x] [0.05] 5.27x10 -6 = x pH = -log [H + ] pH = -log [5.27x10 -6 ] pH = 5.28 .: pH = 5.28 5.27x10 -6 0.05 5.27x10 -6 c) STRONG-WEAK TITRATIONS

40. Calculations In a titration 20.0 mL of 0.1 M NH 3(aq) is titrated with 0.1 M HCl (aq) . What is the pH of the resulting solution after the following volumes of HCl (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL NH 3(aq) + H 2 O (l) <===> OH - (aq) + NH 4 + (aq) d) n NH 3 =CV n NH 3 =(0.1M)(0.020L) n NH 3 =0.002 mol n HCl =CV n HCl =(0.1M)(0.030L) HCl (aq)  H + (aq) + OH - (aq) n HCl =0.003mol n HCl remaining =0.001 mol n NH 3 remaining = 0 mol V total =0.050L C=n/V total C=0.001mol/0.050L C=0.02M n NH 4 + formed = 0.002 mol STRONG-WEAK TITRATIONS

41. Calculations In a titration 20.0 mL of 0.1 M NH 3(aq) is titrated with 0.1 M HCl (aq) . What is the pH of the resulting solution after the following volumes of HCl (aq) have been added? a) 0.00 mL b) 10.0 mL c) equivalence pt d) 30.0 mL NH 3(aq) + H 2 O (l) <===> OH - (aq) + NH 4 + (aq) d) Since we discovered before that the conjugate acid/base formed does not significantly affect pH when a strong acid/base is present, then we can solve for the pH by using the [HCl] HCl (aq)  H + (aq) + OH - (aq) C HCl =0.02M pH = -log [H + ] pH = -log [0.02] pH = 1.69897 .: pH = 1.70 STRONG-WEAK TITRATIONS