Lecture 12 - Electrolytes, Acids and Bases

Lecture 12 - Electrolytes, Acids and Bases - Sep 28, 2011...

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Lecture 12: Electrolytes; Acids and Bases What makes exchange reactions take place? ± •an insoluble insoluble ionic compound •AgNO 3 (aq) + KC l (aq) ĺ KNO 3 (aq) + AgC AgC l (s) ± •O f ten wa te r •H 2 SO 4 (aq) + 2 NaOH(aq) ĺ Na 2 SO 4 (aq) + 2 H 2 O( l ) ± •2 HC l (aq) + Na 2 S(aq) ĺ 2 NaC l (aq) + H 2 S(g) Sep 28, 2011 1-2
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Electrolytes •S om e s o l u t i o n s c o n d u c t e l e c t r i c i t y ± These solutes are called “electrolytes” ± They dissociate into ions •NaC l Æ Na + + Cl - •The ion s in te ra c t w i th the so l ven t (e spe c ia l l y wa r ) ± The extent of solubility varies depending on the balance between interaction of ions with themselves and with water o l u t e s t h a t d o n o t c o n d u c t e l e c t r i c i t y a r e n o n - electrolytes Aqueous Solubility of Compounds Soluble ionic compounds dissociate. Most molecular compounds stay associated in water. Ions are solvated 2-3 2-4
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When ionic solutions mix, a precipitate may form: AgNO 3 (aq) + NaC l (aq) AgC l (s (s ) + NaNO 3 (aq) KNO 3 (aq) + NaC l (aq) No reaction Precipitation Reaction Soluble species: Soluble species: •A l l amm o n i um a n d g r o u p 1A (N a + , K + ,…. and NH 4 + salts) l l n i t r a t e s (NO 3 - ) •M o s t c h l o r i d e s , b r om i d e s a n d i o d i d e s ± (exceptions: AgX, Hg 2 X 2 , and PbX 2 ; X = C l - , Br - , I - ). o s t s u l f a t e s (SO 4 2- ) ± (exceptions: CaSO 4 ,SrSO 4 , BaSO 4 , Ag 2 SO 4 , PbSO 4 , and Hg 2 SO 4 ) l l c h l o r a t e s (C l O 3 - ) l l p e r c h l o r a t e s(C l O 4 - ) l l a c e t a t e s (CH 3 COO - ) Aqueous Solubility of Ionic Compounds 3-2 3-3
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Type Exceptions •A l l p h o s p h a t e s (PO 4 3- ) Group 1A, NH 4 + l l c a r b o n a t e s (CO 3 2- )G r o u p 1 A , N H 4 + l l h y d r o x i d e s (OH - r o u p 1 A , N H 4 + ± Sr(OH) 2 , Ba(OH) 2 & Ca(OH) 2 are slightly soluble l l o x a l a t e s (C 2 O 4 2- ) Group 1A, NH 4 + l l o x i d e s (O 2- r o u p 1 A l l s u l f i d e s(S 2- r o u p 1 A , N H 4 + ± MgS, CaS & BaS are slightly soluble. Aqueous Solubility of Ionic Compounds (a)Nitrates (soluble) AgNO 3 Cu(NO 3 ) 2 CdS Sb 2 S 3 PbS (NH 4 ) 2 S soluble insoluble (c) Sulfides (b) Hydroxides (insoluble) Cu(OH) 2 AgOH Aqueous Solubility of Ionic Compounds 4-1
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Products? Na + SO 4 2- Ba 2+ NO 3 - Precipitation Reactions Na 2 SO 4 (aq) and Ba(NO 3 ) 2 (aq) are mixed. Will they react? NaNO 3 and BaSO 4 . Insoluble? Yes Yes . BaSO 4 –A reac t ion occurs : Na 2 SO 4 (aq) + Ba(NO 3 ) 2 (aq) BaSO 4 (s) + 2 NaNO 3 (aq) Soluble ionic compounds fully dissociate: AgNO 3 (aq) Ag + (aq) + NO 3 - (aq) KC l (aq) K + (aq) + C l - (aq) On mixing: Net Ionic Equations Ag + (aq) + NO 3 - (aq) + K + (aq) + C l - (aq) AgC l (s) + K + (aq) + NO 3 - (aq) K + and NO 3 - appear on both sides ± NO 3 - and K + ions.
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Lecture 12 - Electrolytes, Acids and Bases - Sep 28, 2011...

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