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Department
Biology (Biological Sciences)
Course
BIOL499A
Professor
Blaine Mullins
Semester
Winter

Description
1 2 Chemistry’s contribution to the Olympic games … Acid  base properties of salt solutions Bizarro by Dan Piraro Salt  ionic solid +  2 Cation is not H , anion is neither OH nor O . Examples: NaCl, K 2CO 3 Al(NO )3 3 +  NaCl (s) Na (aq)+ Cl (aq) Salt solution  acidic, basic or neutral ? Read 19.1,9.2 1. Cation effect on pH Practice 2. Anion effect on pH PS 4 is posted online. You can solve Q 1–4 3. Combined effect of the cation and the anion Solutions to term exam 1 will be posted when I get a chance to type them. 3 4 Cation effect Anion effect Cations derived from strong bases (group 1 + heavier Anions derived from strong acids (Cl , Br , I , NO , 3  2 group 2 cations)  no effect ClO 4 SO 4 )  no effect Why ? Why ? +  + Na +    Na + H 2 NaOH + H + H2O Cl + H 2  HCl + OH  Cl + H 2 NaOH is a strong base so it immediately dissociates to HCl is a strong acid so it immediately dissociates to H Na +and OH and the OH and H recombine to form and Cl and the H and OH recombine to form H 2O. H 2. So no reaction for Na and water.  So no reaction for Cl and water. All other cations react with water to yield weakly acidic All other anions react with water to yield weakly basic solutions. solutions. + 3+ NH ,4Transition metals, Al all weakly acidic F– + H O  HF + OH  basic (aq) 2  (aq) (aq) + + NH 4 (aq) H 2  H 3 + NH 3 (aq) weakly acidic 5 6 Combined effect of cations and anions l l a r eno i nAno i t aC Find the pH of a 1M NH 4I solution NH I acidic ------ acidic 4 Complete dissociation NH 4  NH 4 Zn(NO )3 2 acidic ------ acidic I is derived from a very strong acid. KClO 4 ------ ------ neutral  Na 3O 4 ------ basic basic  I + H O  HI + OH – 2  NH F acidic basic ??? 4 HI is a very strong acid and it immediately dissociates, Rarely would the two effects exactly cancel each out HI  H + I – When K a> K b acidic + – H + OH  H O 2 K a< K b basic K a= K b neutral Net reaction: I + H2O  I + H 2 neffect + –10 K aNH )4= 5.5 x 10 Remember: ions derived from strong acids or strong – Kw 1 x 10–14 –11 K bF ) = = –4 = 1.4 x 10 bases have no effect on the pH of the solution. K aHF) 7 x 10 + NH 4s a weak acid and we need to consider its K aNH )4> K (Fb) – acidic dissociation in water. 7 8 + + + NH 4 + H2O  NH 3 H O 3 Ka(NH )4
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