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Chapter 8 Activity

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Homework Chapter 8 - Activity 8.2, 8.3, 8.6, 8.9, 8.10, 8.12

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Question 8.2 Q: Which statements are true? In the ionic strength, , range of M, activity coefficients decrease with: a) increasing ionic strength b) increasing ionic charge c) decreasing hydrated radius All are true!!

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Question 8.3 Calculate the ionic strength of a) M KOH b) M La(IO 3 ) 3 (assuming complete dissociation at low concentration) Remember for +1/-1 systems: Ionic strength, = Molarity, M Ionic strength ( ) = ½ (c 1 z c 2 z …) = ½ [0.0087M(+1) M(-1) 2 ] = M

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Question 8.3 (cont’d) Calculate the ionic strength of a) M KOH b) M La(IO 3 ) 3 (assuming complete dissociation at low concentration) Ionic strength ( ) = ½ (c 1 z c 2 z …) = ½ [0.0002M(+3) M(-1) 2 ] = M

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Question 8.6 Calculate the activity coefficient of Zn 2+ when M by using (a) Equation 8-6 and (b) linear interpolation with Table 8-1. = = a)

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Question 8.6 (cont’d) Calculate the activity coefficient of Zn 2+ when M by using (a) Equation 8-6 and (b) linear interpolation with Table 8-1. =

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Question M KNO 3. Calculate the concentration of Hg 2 2+ in saturated solutions of Hg 2 Br 2 in M KNO 3. Hg 2 Br 2(s) Hg Br - K sp =5.6x ICE some- - -x+x+2x some-x+x+2x

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8-10. Find the concentration of Ba 2+ in a M (CH 3 ) 4 NIO 3 solution saturated with Ba(IO 3 ) 2 (s).+ Ba(IO 3 ) 2 Ba IO 3 K sp = 7.11 x ICE some x+x+2x some-x+x+2x

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8-10. Find the concentration of Ba 2+ in a M (CH 3 ) 4 NIO 3 solution saturated with Ba(IO 3 ) 2 (s).+ Ba(IO 3 ) 2 Ba IO 3 K sp = 1.5 x ICE some x+x+2x some-x+x0.1+2x

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8-10. Find the concentration of Ba 2+ in a M (CH 3 ) 4 NIO 3 solution saturated with Ba(IO 3 ) 2 (s).+ Ba(IO 3 ) 2 Ba IO 3 K sp = 1.5 x ICE some x+x+2x some-x+x0.1+2x X = x 10 -7

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Question 8-12 correctly, Using activities correctly, calculate the pH of a solution containing M NaOH plus M LiNO 3. What is the pH if you neglected activities? ( ) = ½ (c 1 z c 2 z …) = ½ [0.010M(+1) M(-1) M(+1) M(-1) 2 ] = M OH = 0.873pH = A H = [H + ] H

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Question 8-12 (cont’d) correctly, Using activities correctly, calculate the pH of a solution containing M NaOH plus M LiNO 3. What is the pH if you neglected activities? pH = 11.94

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Question 8-12 (cont’d) correctly, Using activities correctly, calculate the pH of a solution containing M NaOH plus M LiNO 3. What is the pH if you neglected activities? pH ~ -log[H + ] =

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Finally Calculate the pH of a solution that contains 0.1 M Acid and 0.01 M conjugate base Calculate the pH of a solution containing 0.1 M Acid and 0.05 M conjugate base. Calculate the pH of a solution containing 0.1 M Acid and 0.1 M conjugate base.

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Acid/Base Titrations

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Titrations Titration Curve – always calculate equivalent point first Strong Acid/Strong Base Regions that require “different” calculations B/F any base is added Half-way point region At the equivalence point After the equivalence point

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Strong Acid/Strong Base 50 mL of M KOH Titrated with M HBr First -find Volume at equivalence M 1 V 1 = M 2 V 2 (0.050 L)( M) = V V = 10.0 mL

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Strong Acid/Strong Base mL of M KOH Titrated with M HBr Second – find initial pH pH = - logA H ~ -log [H + ] pOH = -logA OH ~ -log [OH - ] pH = 12.30

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Strong Acid/Strong Base 50 mL of M KOH Titrated with M HBr Third– find pH at mid-way volume KOH (aq) + HBr (aq) -> H 2 O (l) + KBr(aq) Before After mol mol mol0 mol Limiting Reactant mol pH = 11.8 (~6 ml)

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Strong Acid/Strong Base 50 mL of M KOH Titrated with M HBr Fourth – find pH at equivalence point KOH (aq) + HBr (aq) -> H 2 O (l) + KBr(aq) Before After mol mol 0 mol mol pH = 7.0

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Strong Acid/Strong Base 50 mL of M KOH Titrated with M HBr Finally – find pH after equivalence point KOH (aq) + HBr (aq) -> H 2 O (l) + KBr(aq) Before After mol mol 0 mol mol mol pH = ml Limiting Reactant

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Titration of WEAK acid with a strong base

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Titration of a weak acid solution with a strong base mL of M acetic acid K a = 1.8 x Titrant = M NaOH First, calculate the volume at the equivalence-point M 1 V 1 = M 2 V 2 ( L) M = M (V 2 ) V 2 = L or 25.0 mL

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Titration of a weak acid solution with a strong base mL of M acetic acid K a = 1.8 x Titrant = M NaOH Second, Calculate the initial pH of the acetic acid solution

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Titration of a weak acid solution with a strong base mL of M acetic acid K a = 1.8 x Titrant = M NaOH Third, Calculate the pH at some intermediate volume

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Titration of a weak acid solution with a strong base mL of M acetic acid K a = 1.8 x Titrant = M NaOH Fourth, Calculate the pH at equivalence

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Titration of a weak acid solution with a strong base mL of M acetic acid K a = 1.8 x Titrant = M NaOH Finally calculate the pH after the addition 26.0 mL of NaOH

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