Titrations and titration curves Announcements Wednesday, April 14, 2010 Known concentration MasteringChemistry due dates: Ch 16: Tuesday Apr 20, 11:59pm Ch 17: Tuesday Apr 27, 11:59pm Ch 18: Friday May 7, 11:59pm Unknown concentration Titration curves lab report due next Monday. The report must contain (either as calculations in a spreadsheet cell or typed out with equation editor in the result section): Concentration calculations for each monoprotic acid Ka found two ways for the weak monoprotic acid (using initial conc/pH and using halfway point); % error for each. Ka1 and Ka2 for the diprotic acid (using two midpoints) Calculated pH at the equivalence point for the weak acid, using the more accurate Ka value. Compare this with your experimental pH at the equivalence point (% error). Titration curve: graph of pH vs volume of solution added Strong acid titrated with strong base pH Quiz 3 Wednesday Apr 21 on end of Ch 15 and Ch 16. Vol NaOH added (mL) ch16c Page 1 ch16c Page 2 Strong acid titrated with strong base Weak acid titrated with strong base 50.0 mL HCl of unknown concentration is titrated with 0.150 M NaOH. The titration curve's only inflection point occurs at 40.0 mL of added base. What was the initial HCl concentration? pH What was the initial pH of the HCl solution? Vol NaOH added (mL) HA + OH− → What is the pH after 60.0 mL NaOH is added? Buffer region: At the midpoint (half-equivalence pt): ch16c Page 3 ch16c Page 4 Weak acid titrated with strong base Weak acid titrated with strong base 40.0 mL of 0.0788 M HA are titrated with 0.100 M NaOH. What is the volume of NaOH added at the equivalence point? What is the pH after 10.0 mL 0.100 M NaOH is added to 40.0 mL of 0.0788 M HA (the titration on the last page)? If the pH = 4.88 at the midpoint, what is Ka and what is the pH at the endpoint? ch16c Page 5 ch16c Page 6 Weak acid titrated with strong base Weak acid titrated with strong base 75.0 mL of a weak acid are titrated by 0.125 M NaOH. The endpoint occurs at 62.1 mL of added base, and the pH at the midpoint is 3.12. What is the initial acid concentration? What is the Ka? What is the pH initially and at the equivalence point? 75.0 mL of a weak acid are titrated by 0.125 M NaOH. The endpoint occurs at 62.1 mL of added base, and the pH at the midpoint is 3.12. What is the initial acid concentration? What is the Ka? What is the pH initially and at the equivalence point? ch16c Page 7 ch16c Page 8 Weak base and polyprotic acid titrations Weak base titr by strong acid pH Vol HCl added (mL) Polyprotic acid titr by strong base pH Vol NaOH added (mL) ch16c Page 9 ch16c Page 10
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