chapter_16_handouts

chapter_16_handouts - Acid-Base Equilibria and Solubility...

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4/27/2009 1 Acid-Base Equilibria and Solubility Equilibria Chapter 16 Titrations In a titration a solution of accurately known concentration is added gradually added to another solution of unknown concentration until the chemical reaction between the two solutions is complete. Equivalence point – the point at which the reaction is complete Indicator – substance that changes color at (or near) the substance that changes color at (or near) the equivalence point Slowly add base to unknown acid UNTIL The indicator changes color ( pink ) 4.7 The titration curve of a strong acid with a strong base. 16.5 Strong Acid-Strong Base Titrations NaOH ( aq ) + HCl ( aq ) H 2 O ( l ) + NaCl ( aq ) OH - ( aq ) + H + ( aq ) H 2 O ( l ) 16.4
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4/27/2009 2 Exactly 100 mL of 0.10 M HNO 2 are titrated with a 0.10 M NaOH solution. What is the pH at the equivalence point ? HNO 2 ( aq ) + OH - ( aq ) NO 2 - ( aq ) + H 2 O ( l ) start (moles) end (moles) 0.01 0.01 0.0 0.0 0.01 NO 2 - ( aq )+H 2 O ( l ) OH - ( aq ) + HNO 2 ( aq ) [NO 2 - ] = 0.01 0.200 = 0.05 M Final volume = 200 mL ) + H OH ( Initial ( M ) Change ( M ) Equilibrium ( M ) 0.05 0.00 - x + x 0.05 - x 0.00 + x xx K b = [OH - ][HNO 2 ] [NO 2 - ] = x 2 0.05- x = 2.2 x 10 -11 0.05 – x 0.05 x 1.05 x 10 -6 = [OH - ] pOH = 5.98 pH = 14 – pOH = 8.02 Weak Acid-Strong Base Titrations CH 3 COOH ( aq ) + NaOH ( aq ) CH 3 COONa ( aq ) + H 2 O ( l ) CH 3 COOH ( aq ) + OH - ( aq ) CH 3 COO - ( aq ) + H 2 O ( l ) CH 3 COO - ( aq ) + H 2 O ( l ) OH - ( aq ) + CH 3 COOH ( aq ) At equivalence point (pH > 7): 16.4 Strong Acid-Weak Base Titrations HCl ( aq ) + NH 3 ( aq ) NH 4 Cl ( aq ) NH 4 + ( aq ) + H 2 O ( l ) NH 3 ( aq ) + H + ( aq ) At equivalence point (pH < 7): H + ( aq ) + NH 3 ( aq ) NH 4 Cl ( aq ) 16.4 16.4
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4/27/2009 3 16.4 The common ion effect is the shift in equilibrium caused by the addition of a compound having an ion in common with the dissolved substance.
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This note was uploaded on 01/31/2010 for the course CHEMISTRY 51 taught by Professor Entus,r during the Fall '09 term at Mt. SAC.

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chapter_16_handouts - Acid-Base Equilibria and Solubility...

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