IMG_0005_NEW_0015

IMG_0005_NEW_0015 - Acidic Solutions Sesond type Highly...

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r) 2) Salts That Produce Acidic Solutions Cation = conjugate acid of weak base? Anion has no effect? = Acidic solution vttnk *) e4ut'{'r P4 P;ample: NHoBr NHnBr(aq) -+ b'vt Cation: NH4*: conjugate acid of a weak base NHn*(aq) Anion: HBr: strong acid = Br has no affinity for H* lslr(aq) --> H*(aq) + Br-(aq) br =&!Ect ogBIL Typical problem: Calculate the pH of a 0.25 M NHoBr solution Salts That Produce Basic Solutions 1) Anion = conjugate base of weak acid? 2) Cation has no effect? + Basic solution Example: KCI{3COO KCH3COO(nq) --> K*(aq) + CH,COO{aq) Anion: CH3COO-: conjugate base of a weak acid CHTCOO-(aq1 + }{[email protected]) - CH3COOH(aq) + OH-(aq) Cation: KOH: strong base + K+ has no afhnity for OH- KOH(aq) -+ K+(aq) + OH-(aq) = No effect on pH pH Calculation: use same approach as for salts that produce acidic solutions. See example 7.11 in text book 6 r-rfr\u{t?N,tt)- 2,t></'2 htort's = z1xro-7 +Br(aq) 0-w I giuen that Kn for NH. : 1.8 x 10-5 L lS'TnI &:&= H =# g o.tt-t { v Salts That Produce
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Unformatted text preview: Acidic Solutions Sesond type: Highly charged metal ions Example: AlCl3 -+ acidic solution AlCl3 -+ Al3*(aq) + Cl-(aq) Al3* is not a Brsnsted-Lowery acid: cannot donate a proton! BUT: Hvdrated cation = weak acid "/"'. r')" l'. \\ o ,/t "-L"f. .J=-" '=-,rt'-''=" : lo\ H ,/\ H Al(HrO)u3*(aq) : Al(OHXH2O)s2*(aq) + U*(aq) Metal ion charge polarizes O-H bonds in water molecules + protons more acidi" , What if both ions contribute to the pH? . Qualitatively: Acidic, Basic or Neutral? > Compare Ku of acidic ion with Ko of basic ion E- If Ku>K6thenpH<7 =Acidic I - IfK"<KothenpH>7 =Basic L - If Ku:Ksthen pH: 7 :> Neutral Remember: Kux Ko: K* . Quantitatively: pH Calculation: 1) Consider acid-base equilibria 2) AND reaction between acid and basic ions 3) Compare K of the acid-base reaction with Ku's and Ko's Whichever dominates -) use to calculate pH . Example: NH*CN dr$or.l, ' AuA-94-B65e fu>tc *Luii"t1...
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