【正文】 depression constant for water is K?mol1?kg1, and for aqueous solution, molarity and molality can be taken as approximately equal. Solution According to f f BT iK b?? ,then f 11fB[ 2 7 3 . 1 5 ( 0 . 5 6 ) ] K 2 7 3 . 1 5 K 31 . 8 6 K k g m o l 0 . 1 m o l k gTi Kb ??? ? ? ?? ? ?? Thus, the plex in the problem is [Co(NH3)4(H2O)2Cl]Cl2. 2. Given the Ks values of [CuY]2 and [Cu(en)2]2+ are 51018 and 1021 respectively, try to determine which of the two plexes is more stable. Solution For [CuY]2, the number of ligand is 1, for [Cu(en)2]2+, the number of ligand is 2, their stability are different. For [CuY]2, C u 2 + + Y 4 [ C u Y ]2 x 1 x 1 0 .1 0 － x 1 = 0 .1 0 m o lL 1 22 1 8s 2 4 21[ C u Y ] 0 . 1( [ C u Y ] ) 5 1 0[ C u ] [ Y ] ( )K x????? ? ? ? x1 = 1010molL1 16 For [Cu(en)2]2+, C u 2 + + 2 e n [ C u ( e n ) 2 ] 2 + x 2 2 x 2 0 . 1 0 － x 2 = 0 . 1 m o l L 1 22 2 12s2 2 2 222[ C u ( e n ) ] 0 . 1( [ C u ( e n ) ] ) 1 . 0 1 0[ C u ] [ e n ] ( 2 )K xx???? ? ? ?? x2 = 108molL1 [CuY]2 is the more stable than [Cu(en)2]2+ because of x2x1. 3. Add 100mL of L1 NaCl solution into 100mL of L1AgNO3 containing excessive ammonia to produce no precipitate of AgCl. Calculate the concentration of ammonia (at least) in mixture solution. Solution 10sp (A gC l) 1. 77 10K ???， 7s 3 2([A g( N H ) ] ) 10K ? ?? [ A g ( N H 3 ) 2 ] 2 + + C l A g C l + 2 N H 30 . 0 5 0 . 0 5 aI n i t i a t i o n o f t h e r e a c t i o n 233 2 s sp27 1 0[ NH ] 1[ A g ( NH ) ] [ C l ]1 5 .1 3 6 1 01 .1 1 0 1 .7 7 1 0K KK?????? ? ?? ? ? To no precipitation of AgCl ??? then 2 1 2 2 1 1( 0 .0 5 ) m o l L ( 0 .0 5 ) 5 .1 3 6 1 0 m o l L 1 .1 3 3 m o l LaK ? ? ?? ? ? ? 4. Explain by calculation whether or not the precipitate AgI will form when c([Ag(CN)2])=c(CN)=L1 in a solution and the solid KI is added to the solution to make c(I) equal to L1. Solution 17sp (A gI) 2 10K ???， 21s2([A g( C N ) ] ) 10K ? ?? [ A g ( C N ) 2 ] + I A g I + 2 C N 0 . 1 0 . 1 0 . 1I n i t i a t i o n o f t h e r e a c t i o n 22 s sp62 1 1 7[ C N ] 1[ A g ( C N) ] [ I ]1 9 .0 3 1 01 .3 1 0 8 .5 2 1 0K KK???????? ? ?? ? ? 17 2 6( 0 .1 ) 1 9 .0 3 1 00 .1 0 .1QK ?? ? ? ? ?? No AgI precipitate forms in the solution. 5. Given the Ks values of [Ag(NH3)2]+ and [Ag(CN)2] are 107 and 1021 respectively, try to determine the direction of the following reaction. [ A g ( C N ) 2 ] + 2 N H 3 [ A g ( N H 3 ) 2 ] + + 2 C N 223 2 3 2 2 22 3 2 37 15s 3 221s2[ A g(NH ) ] [ C N ] [ A g(NH ) ] [ C N ] [ A g ]S ol ut i on [ A g(C N) ] [ NH ] [ A g(C N) ] [ NH ] [ A g ]( [ A g(NH ) ] ) 10 10( [ A g(C N) ] ) 10KKK? ? ? ? ????????? ? ??? ? ? ?? The reaction is in reverse direction. [ A g ( N H 3 ) 2 ] + + 2 C N [ A g ( C N ) 2 ] + 2 N H 36. A Cu electrode is immersed in a solution that is ?L1 NH3 and ?L1 in [Cu(NH3)4]2+. If a standard hydrogen electrode is the cathode, celE is + V. what is the value obtained by this method for the formation constant, fK , of [Cu(NH3)4]2+? Solution The cell in the problem is as follows: 2 1 13 4 3( ) Cu | [ Cu ( N H ) ] ( 1 .0 0 m o l L ) , N H ( 1 .0 0 m o l L ) || SH E ( )? ? ??? 22c e l l SH E 3 4 3 4( [ Cu ( N H ) ] / Cu ) ( [ Cu ( N H ) ] / Cu ) 0 .0 5 2 VE ? ? ???? ? ? ? ? 234( [ C u( N H ) ] / C u ) 52 V? ? ?? 22 θ 2 343 4 3 4 43θ 234 4θ 234( [ C u( N H ) ] )( [ C u( N H ) ] / C u ) ( [ C u( N H ) ] / C u ) l g2 ( N H ) 916 ( [ C u( N H ) ] / C u ) l g2 ( )( [ C u( N H ) ] / C u ) 2 Vcc???????????????? θ 2 θ 23 4 ss 16( [ C u( N H ) ] / C u ) ( C u / C u ) l g2 9 V l g2 VKK?? ???????? s 2 [ 0 . 3 4 1 9 V ( 0 . 0 5 2 V ) ]l g 1 3 . 3 20 . 0 5 9 1 6 VK ? ? ???， 13s 10K ??。 7. The following concentration cell is constructed. 1 1 12A g | A g ( 0 .1 m o l L [ A g ( CN ) ] , 0 .1 m o l L CN ) || A g ( 0 .1 m o l L ) | A g? ? ? ? ? ? ? 18 If sK for [Ag(CN)2] is 1021, what value you expect for celE ? [Hint: Recall that the anode is on the left.] Solution Cathode θ( A g / A g ) ( A g / A g ) 59 16 l g ( A g )c??? ? ??? Anode θ22 2θs 2( [ A g( C N) ] )( [ A g( C N) ] / A g ) ( [ A g( C N) ] / A g ) 16 l g( C N )( [ A g( C N) ] )( A g / A g ) 16 l g 16 l g( C N )cccKc??????????? ? ? c e ll 2θθ 2s2 2212( A g / A g ) { [ A g ( CN) ] / A g }( A g / A g ) 0 .0 5 9 1 6 lg ( A g ){ [ A g ( CN) ] } ( A g / A g ) 59 16 lg { [ A g ( CN) ] } 5 9 1 6 lg( CN )0 .1 0 .0 5 9 1 6 lg 0 .1 0 .0 5 9 1 6 lg ( 1 .2 6 1 0 ) 0 .0 5 9 1 6 lg( 0 .1 )1 .1 3EccKc??????????????? ? ?? ? ? ?? 0V