Gen Chemistry Chap 19 notes
Gen Chemistry Chap 19 notes 603613
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This 3 page Class Notes was uploaded by Emmanuel Notetaker on Sunday March 6, 2016. The Class Notes belongs to 603613 at University of Cincinnati taught by waddell, D in Winter 2016. Since its upload, it has received 33 views. For similar materials see Gen Chem II in Chemistry at University of Cincinnati.
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Date Created: 03/06/16
Gen Chem Chap 19: Ionic Equilibria in Aqueous System What is a buffer solution? Twocompound solutes that resist change in pH when acid or base are added. They maintain a narrow pH range. How many minimum components must an effective buffer contain? Two: one for H+, other for OH What are the two main types of buffers? Weak acid + its conjugate base Weak base + its conjugate acid Write two balance net equations showing how a buffer composed of nitrous acid and potassium nitrite works HNO2 + OH = H2O + NO2 NO2 + H+ = HNO2 Explain why a solution of sodium chloride and hydrochloric acid is not a buffer solution HCl is a strong acid, buffers require weeklies Explain why a solution formed by mixing 100 ml of a 0.100 M acetic acid with 50 ml of 0.100 M sodium hydroxide solution will act as a buffer solution HAc + OH = Ac +H2O Given concentrations results in 50% HAc and 50% Ac balanced buffer system Write the HandersonHasselbalch equation for a weak acid/conjugate base buffer system PH =pKa + log [Conj base/weak acid] Write the HandersonHasselbalch equation for a weak base/ conjugate acid buffer system POH= pKb + log [conj acid/weak base] What law was the HendersonHasselbalch equation derived from? Ans: Law of mass action What is the principle application for the HendersonHasselbalch Equation? Buffer Solutions Equivalence point Theoretical point during titration when reaction reaches stoichiometric completion End Point Experimental approximation of equivalence point when indicator changes color Titration Carefully measured and controlled addition of one solution of known concentration (STD) to another solution whose concentration is to be determined with the amount it reacts What is a buffer capacity? Measure of capacity of buffer to resist changes in PH. Related to the concentrations of the two components What is the effective range for most buffers? Why? Effective range is +/ 1.0 pH unit from target PH. Reason: beyond CB/WA ratios of 10/1 to 1/10 system won’t work What is a titration curve? Plot of change in pH vs. amount of base or acid added during the titration Acidbase buffer A solution that resists changes in pH when a small amount of either strong acid or strong base is added Commonion effect The shift in the position of an ionic equilibrium away from an ion involved in the process that is caused by the addition or presence of that ion