Lecture 5-acid-base

Lecture 5-acid-base - Chemistry 271, Fall 2009 General...

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Chemistry 271, Fall 2009 General Chemistry and Energetics Lectures #5 and #6: Acids, Bases, p H , pK a , pK b , K w , Titrations, Calculations, Henderson- Hasselbach, Buffers September 16, 2009 Jason D. Kahn Dept. of Chemistry and Biochemistry jdkahn@umd.edu
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Lecture 5: Acid-Base, Chemistry 271, Fall 2009, Jason Kahn Course Mechanics SmartWork Assignment due 11:55 p.m. tonight. Answer Key #1 will be available tomorrow. My office hours are 2:00-3:00 p.m. today. If you did not receive an email about add/drop, please email me. Reading: Chapter 16 (Lewis acids and bases are in chapter 17) Problems for Chapter 16: 1, 3, 7, 14, 30, 45, 50, 54, 64, 86, 113
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Lecture 5: Acid-Base, Chemistry 271, Fall 2009, Jason Kahn Importance of Acid-Base Equilibria Acid-base equilibria are fundamental to all of chemistry and biochemistry. Control of pH and the use of buffers have widespread practical implications. If you are doing any biochemical experiment, you should either be controlling the pH, measuring the pH, or both. Enzymes often act by donating or removing protons. Acid rain and the decreasing alkalinity of the oceans are serious environmental problems. Blood pH control is important for oxygen and CO 2 transport.
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Lecture 5: Acid-Base, Chemistry 271, Fall 2009, Jason Kahn Acid-base topics Increasingly general definitions of acids and bases (Arrhenius Brønsted-Lowry Lewis). Strong acids and bases vs. weak acids and bases Relevant equilibria for acid-base reactions pH, K a , p K a , K b , p K b , K w Rationalizing p K a s based on the chemical properties of acids and their conjugate bases Calculations: Degree of dissociation, distribution among species, and pH throughout titrations. Equivalence points. Principal and subsidiary dissociation reactions. Buffers and the Henderson-Hasselbach relationship Buffering in the blood Polyprotic acids, isoelectric points.
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Lecture 5: Acid-Base, Chemistry 271, Fall 2009, Jason Kahn What are acids and bases? Arrhenius definition: Acids dissolve in water to yield H + (H 2 SO 4 ) Bases dissolve in water to give OH - (NaOH) Brønsted-Lowry definition: Acids transfer (donate) protons Bases accept protons (NH 3 ; more general)
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Lecture 5: Acid-Base, Chemistry 271, Fall 2009, Jason Kahn Follow the protons! Water acting as a base accepts a proton from an acid HA to give the hydronium ion and a deprotonated A - . HA and A - are a conjugate pair , as are H 2 O and H 3 O +
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Lecture 5: Acid-Base, Chemistry 271, Fall 2009, Jason Kahn Water can be an acid or a base Water acting as an acid donates a proton to a base B in solution, giving hydroxide ion HO - and protonated BH + .
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Lecture 5: Acid-Base, Chemistry 271, Fall 2009, Jason Kahn Water self-dissociation The reaction H 2 O(l) + H 2 O(l) H 3 O + (aq) + HO (aq) is called the dissociation of water. We usually absorb the concentration of water into
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This note was uploaded on 01/24/2011 for the course CHEM 271 taught by Professor Staff during the Spring '08 term at Maryland.

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Lecture 5-acid-base - Chemistry 271, Fall 2009 General...

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