TUZLAR ERITMALARINING GIDROLIZI


Tuz  ionlarining  suv bilan ta’sirlashib kuchsiz elektrolit hosil qilish reaksiyasiga tuzlar gidrolizi deyiladi.     Barcha tuzlarni ularni hosil qilgan asos va kislotaning kuchiga qarab to’rtga bo’lish mumkin.

  1. Kuchli  asos  va  kuchli  kislotalardan hosil bo’lgan tuzlar gidrolizga uchramaydi, ya’ni ularning ionlari suv bilan ta’sirlashib kuchsiz elektrolitlar hosil qilmaydi.
  2. Kuchsiz asos va kuchli kislotadan hosil bo’lgan tuzlar kation bo’yicha  gidrolizlanadi,  eritma muhiti kislotali bo’ladi.  Agar kuchsiz asos bir kislotali bo’lsa, gidroliz reaktsiyasi bir bosqichdan iborat bo’lib, bunda kuchsiz asos va kuchli kislota hosil bo’ladi.

     NH4Cl + H2O = NH4OH + HCl

     NH4 + Cl + H2O = NH4OH + H + Cl-

     NH4+  + H2O = NH4OH + H+                      muhit kislotali, pH < 7.

     Agar kuchsiz asos ko’p kislotali bo’lsa,  gidroliz bosqichli bo’ladi. 1-bosqichda asosli tuz va kuchli kislota hosil bo’ladi.

1-bosqich: AlCl 3  + H2O = AlOHCl+ HCl

          Al3+  + 3Cl -  + H2O = AlOH 2+  + 2Cl -  + H +  + Cl -

          Al 3+  + H2O = AlOH2+  + H +                pH < 7

     Gidroliz reaktsiyasi qaytar bo’lib, qisman sodir bo’ladi. Gidrolizning 2-  va 3-bosqichlari eritmani suyultirganda,  hamda qizdirganda sodir bo’lishi mumkin.

2-bosqich: AlOHCl2  + H2O = Al(OH)2Cl + HCl

          AlOH2+  + 2Cl-  + H2O = Al(OH)2+  + Cl + H+  + Cl-

          AlOH2+  + H2O = Al(OH)22+  + H +

3-bosqich: Al(OH) Cl + H2O = Al(OH)+ HCl

          Al(OH)21+  + Cl + H2O = Al(OH) + H +  + Cl-

          Al(OH)21 +  + H2O = Al(OH)3  + H +

     Eritmada vodorod ionlari kontsentrasiyasining ortishi gidrolizning 2- va 3-bosqichlarining borishiga to’sqinlik qiladi.

  1. Kuchli asos va kuchsiz kislotadan hosil bo’lgan tuzlar anion bo’yicha gidrolizlanadi,  eritma muhiti ishqoriy bo’ladi. Agar kuchsiz kislota bir asosli bo’lsa, gidroliz reaktsiyasi bir bosqichdan iborat bo’lib, bunda kuchli asos va kuchsiz kislota hosil bo’ladi.

          CH3COONa + H2O = CH3COOH + NaOH

          CH3COO+ Na  +   0H -+H2O = CH3COOH + Na+  + OH-

          CH3COO-  + H2O = CH3 COOH + OH -      muhit ishqoriy, pH > 7

                 Al2(SO4)3  ko’p negizli asoslar ham bosqichli gidrolizga uchraydi:

                   Al2(SO4)3 + 2H2O  = 2AlOHSO4  + H2SO4

                   Al3+ + H2O =   AlOH 2+ +H+

                 2 AlOHSO4 + 2H2O = [Al(OH)2]2SO4 + H2SO4

                 AlOH2+ + H2O = [Al(OH)2]2+  + H+

                 [Al(OH)2]2SO4 + 2H2O= 2Al(OH)+ H2SO4

                 [Al(OH)2]2+  +H2O= 2Al(OH)3  + H+

     Agar kuchsiz kislota ko’p asosli bo’lsa,  gidroliz bosqichli bo’ladi. 1-bosqichda kuchli asos va nordon tuz hosil bo’ladi.

1-bosqich: Na2CO3 + H2O = NaOH + NaHCO3

          2Na +  + CO32-  + H2O = Na+  + OH  + Na +  + HCO3-

          CO32-  + H2O = OH -  + HCO3                   pH > 7

     Reaktsiyaning 2-bosqichi  eritmani suyultirganda yoki qizdirganda sodir bo’ladi.

2-bosqich: NaHCO3 + H2O = NaOH + H2CO3

          Na + + HCO3+ H2O = Na + + OH - + H2CO3

          HCO3-  + H2O = OH + H2CO3

Uch  nasosli kislotalar uchta bosqichda gidrolizga uchraydi:

K3PO4 + H2O = K2HPO4+ KOH

 3K++PO43- + H2O =  K++OH- + 2 K+ + HPO42-

  PO43- + H2O       =    OH- + HPO42-

  K2HPO4+ H2O       =   K H2PO4+ KOH

 2 K ++  HPO42- + H2O       =   K ++H2PO4+ K+ + OH-

      HPO42- + H2O       =   H2PO4+  + OH-

   KH2PO4+ H2O       =    H3PO4+ KOH

     K+ +   H2PO4- + H2O       =   H3PO4 + K+ + OH-

    H2PO4- + H2O       =   H3PO4+  OH-      

  1.  Kuchsiz asos va kuchsiz kislotadan hosil bo’lgan tuzlar ham kation, ham  anion  bo’yicha gidrolizlanadi.  Eritma muhiti neytral yoki kislota va asosning nisbiy kuchiga qarab kuchsiz kislotali  yoki ishqoriy bo’lishi mumkin.

          CH3COONH4 + H2O = CH3COOH + NH4OH

          CH3COO -  + NH4+  + H2O = CH3COOH + NH4OH

     Bunday tuzlar eritmalarida muhit deyarli neytral bo’ladi.  Ko’pchilik gidrolizlanish reaksiyalari  qaytardir.  Agar  gidroliz natijasida cho’kma yoki gaz modda hosil bo’lsa,  bunday gidroliz   to’la  gidroliz  deyiladi. Chunki bu holda reaksiya qaytmas bo’lib oxirigacha boradi.

               Al2S  + 6H2O  =  Al(OH)3 + 3H2S

          Al2(CO3)3  +  6H2O   = 2Al(OH)+ 3H2CO3

     Shuning uchun ham Al2Sva Al2(CO3) larning eritmalari mavjud emas, ularni faqat  quruq holda olish mumkin.

  1. Kuchli asos hamda kuchsiz kislotadan hosil  bo’lgan  tuz  va kuchsiz asos  hamda kuchli kislotadan hosil bo’lgan tuzlar eritmalarini aralashtirganimizda ular bir-birining gidrolizlanishini kuchaytiradi. Chunki  bunda  hosil bo’layotgan H+  va OH-  o’zaro birikib suv hosil bo’ladi va muvozanat o’ngga siljiydi.  Bunday gidrolizni birgalikdagi gidroliz deyiladi.    
  2.    Birgalikdagi gidroliz

     Agar gidroliz jara’yonida bir nechta tuz ishtirok etsa gidroliz oxirigacha boradi:     

            2AlCl3 + 3Na2CO+ 3H2O = 2Al(OH)3 +6NaCl + 3CO2 

             2Al3+ + 3CO32- + 3H2O = 2Al(OH)3 + 3CO   

          Bu jarayonda AlCl3 o’rniga    Al2(SO4)3;  CrCl3;  Fe(NO3)3;

          BiCl3; Fe2(SO4)3 larni olish mimkin.

          Na2CO o’rniga  K2CO3, Li2CO3  o’xshash karbonatlarni olsa bo’ladi.

          Agar gidroliz jarayoni  CuSO4  ishtirokida olib borilsa:

            2CuSO4 + 2K2CO3+H2O = (CuOH)2CO3  + 2K2SO4 + CO2

                  2Cu2+ + 2CO32-  +H2O = (CuOH)2CO3 + CO2

 

         Bu gidroliz jarayonida CuSO4 o’rniga MgSO4, BeSO4 olish mumkin.

         Gidroliz jarayonida  karbonatlar o’rniga ,sulfidlar, asetatlar ham olsa bo’ladi:

           2FeCl3 + 3Na2S + 6H2O = 2Fe(OH)3 + 6NaCl + 3H2S

            2Fe3+ + 3S2- + 6H2O = 2Fe(OH)+ 3H2S

          2Al(NO3)3 + 6CH3COONa + 6H2O = 2Al(OH)3 + 6CH3COOH + 6NaNO3

 

      3K2CO3 + Al2 (SO4)3  + 3H2O = 2Al(OH)3 + 3K2SO4 + 3CO2

6K + + 3CO32- + 2Al3+  + 3SO42- + 3H2O = 2Al(OH)3 + 6K + 3SO4 2- + 3CO 2

             3CO3 2-  + 2Al3+  + 3H2O = 2Al(OH)3 + 3CO2

 

     3Na2S + Cr(SO4)3  + 6H2O = 2Cr(OH)3 + 3H2S + 3Na2SO4

6Na+  + 3S 2- + 2Cr3+  + 3SO2-  +6H2O = 2Cr(OH)3 + 3H2S+6Na + +3SO42-

              3S2-  + 2Cr3+  + 6H2O = 2Cr(OH)3 + 3H2S

                      GIDROLIZ KONSTANTASI

     Gidroliz reaksiyasi  qaytar bo’lganligi uchun unda muvozanat qaror topadi. Muvozanatga massalar ta’siri qonunini tatbiq etamiz.

     Masalan: kuchsiz kislota va kuchli asosdan hosil bulgan tuz

       CH3 COO-  + H2O = CH3 COOH + OH – 

      

        [CH3COOH]*[OH-]                                         [CH3COOH]*[OH-]

 K= ---------------------------;          Kg=K*[H2O]= ---------------------------

        [CH3COO-]*[H2O]                                               [CH3COO-]

 

Shu tenglamani surat  va maxrajini [H+] ga ko’paytirsak:

                             [CH3COOH]*[OH-]*[H+]      [OH-]*[H+]

                     Kg=---------------------------   =      --------------

                                 [CH3COO-]*[H+]                   Kkis

 

[OH-]*[H+]=Kw  qiymat suvning ion kopaytmasi ekanligi hisobga olinsa

                                    Kw

                    Kg=---------------------

                                    Kkis

   Agar                     NH4Cl+H2O=NH4OH+HCl

                                NH4+ + H2O  =  NH4OH  +H +

                                [ NH4OH]*[H +]

                 Kg=     --------------------  

                                 [ NH4+

 

    Bu tenglamani ham surat  va maxraji [OH-] ga ko’paytirilsa, unda

                            

                                [ NH4OH]*[H +]*[OH-]       [H +]*[OH-]

                 Kg=     ----------------------------     =  --------------

                               [ NH4+]*[OH-]                        K asos

 

                                                Kw

                                Kg=  ---------------;

                                               K asos

       Tuzning gidroliz  konstantasi asos yoki kislotaning dissotsiyalanish konstantasi qancha  kichik bolsa yuqori bo’ladi.

       Agar tuz kuchsiz asos va kuchsiz kislotadan tashkil topgan bo’lsa  gidroliz konstantasi

          CH3COO -  + NH4+  + H2O = CH3COOH + NH4OH

                            [ CH3COOH] * [ NH4OH]

                  Kg=---------------------------------- ;

                              [ CH3COO -]*[ NH4+

      Agar bu tenglama [H+]*[OH-] ga ko’paytirilsa:

                                               

                          [ CH3COOH] *[ NH4OH]* [H+]*[OH-]        [H+]*[OH-]

                  Kg=-------------------------------------------------= ------------------

                              [ CH3COO -]*[ NH4+] [H+]*[OH-]            Kkis*Kasos

 

                                                [H+]*[OH-]              Kw

                                      Kg=------------------= ------------

                                                 Kkis*Kasos            Kkis*Kasos                                                     

                                                Kw

                               Kg=-------------------

                                              Kkis*Kasos

 

             Bu tenglamaga ko’ra kislota va asosnong dissotsilanish konstantasi qancha  kichik bo’lsa uning gidrolizlanish konstantasi shuncha yuqori bo’ladi.

                            Gidrolizlanish darajasi

     Kuchli asos va kuchsiz kislotadan hosil bo’lgan tuzlarnong gidrolizini ko’raylik.

                   CH3COONa  +H2O =  CH3COOH + NaOH

                    CH3COO- +    +H2O =  CH3COOH + OH-

                     ( 1-b)*C                              bC               bC

                               [ CH3COOH]  [OH-]        bCbC             b2

                    Kg=-----------------------------= --------------=----------

                                  [CH3COO-]                    ( 1-b)*C      ( 1-b)

 

                                     b2C                                                                        Kg

                          Kg=--------------;            1  -  b  =  1     Kg= b2C  ;  b2=-------- 

                                    ( 1-b)                                                                      C

 

                   Demak,   gidroliz darajasi kuchli asos va kuchsiz kislotadan hosil bo’lgan tuzning  konsentrasiyasi qancha kichik bo’lsa gidroliz darajasi yuqori bo’ladi.   

                       NH4Cl+H2O= NH4OH + HCl 

                        NH4+   +H2O  =   NH4OH + H+ 

                       (1- b)C                     bC        bC

 

                   [NH4OH] *[ H+]        bC   bC              b2C2            b2C    

         Kg= -------------------  = ---------------=  -------------= --------------

                     [NH4+]                                (1- b)C             (1- b)C         (1- b)    

 

                                  b2C                                                                Kg

                     Kg=------------------;       (1- b) =1 ;      b2C =Kg ;  b2=-----        

                                 (1- b)                                                              C

               Kuchsiz asos bilan kuchli kislotadan iborat bo’lgan tuzlar uchun   gidroliz darajasi  tuzning konsentrasiyasiga  teskari bog’langan. Eritma qancha suyultirilgan bo’lsa gidroliz  shuncha tez boradi.

              Agar asetat ammoniyning gidrolizlanishi hisobga olinsa , CH3COONH4

Bu modda ham anion va ham kation bo’yicha gidrolizga uchraydi:

         CH3COONH4  +  H2O =  CH3COOH  +  NH4OH

         CH3COO- + NH4+ + H2O =  CH3COOH +  NH4OH

                b C          bC                     (1-  b)*C      (1- b )*C

                                                    Kw           (1-  b)*C* (1- b )*C       ( 1-b)2

                                        Kg= -----------= --------------------------=    -------

                                                  Kas*Kkis          b C*  bC                       b2

 

                                                  ( 1-b)2               ( 1-b)2            Kw   

                                        Kg= -----------;         ----------= ---------

                                                    b2                       b2            Kas*Kkis

 

     Demak, gidroliz darajasi kuchsiz asos va kuchsiz kislota uchun  eritma konsentrasiyasiga bog’liq emas.

      Gidroliz jarayoni  farmasiyada katta ahamiyatga ega. Ko’pgina dori moddalari eritmada tayyorlanadi.Masalan. yiringli yaralarni tuzatish uchun Pb(NO3)2 ishlatiladi. Bu tuz gidrolizlanishi tufayli PbOHNO3 hosil bo’lib asosiy ta’sir etuvchi modda ana shu hisoblanadi.                 

Birikmalari
  • H2O - Suv
  • HN 3 - Amiak
  • HF - Vodorod ftorid
  • HCl - Vodorod xlorid
  • NaH - Natriy gidrid
  • MgH 2 - Magniy girid
  • KH - Kaliy girid
  • BaH 2 - Bariy gidrid
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