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Beberapa gram amonia  0,25 M, pH-nya 11+ log 2 dir...

Beberapa gram amonia begin mathsize 14px style open parentheses N H subscript 3 close parentheses end style 0,25 M, pH-nya 11+ log 2 direaksikan dengan larutan asam formiat (HCOOH) 0,09 M yang pH-nya 3 - log 6. Hitunglah :

Derajat hidrolisis garam begin mathsize 14px style H C O O N H subscript 4 end style dalam larutan 0,15 M tersebut!

Jawaban:

Untuk menghitung derajat hidrolisis garam begin mathsize 14px style H C O O N H subscript 4 end style langkah yang pertama yaitu menentukan Ka HCOOH dan kb begin mathsize 14px style N H subscript 3 end style 

Ka HCOOH dihitung berdasarkan nilai pH-nya 3 - log 6 yang mempunyai konsentrasi 0,09 M yaitu sebagai berikut:

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row pH equals cell 3 minus sign log space 6 end cell row cell H to the power of plus sign end cell equals cell 6 cross times 10 to the power of negative sign 3 end exponent M end cell row cell H to the power of plus sign end cell equals cell square root of Ka cross times 0 comma 09 M end root end cell row cell 6 cross times 10 to the power of negative sign 3 end exponent M end cell equals cell square root of Ka cross times 0 comma 09 M end root end cell row Ka equals cell fraction numerator open parentheses 6 cross times 10 to the power of negative sign 3 end exponent M close parentheses squared over denominator 9 cross times 10 to the power of negative sign 2 end exponent M end fraction end cell row blank equals cell 6 comma 67 cross times 10 to the power of negative sign 5 end exponent M end cell end table end style  

Berikutnya menentukan Kb begin mathsize 14px style N H subscript 3 end style 0,25 M pH = 11 + log 2 sebagai berikut:

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row pH equals cell 11 plus log space 2 end cell row pOH equals cell 14 minus sign left parenthesis 11 plus log space 2 right parenthesis end cell row blank equals cell 3 minus sign log space 2 end cell row cell O H to the power of minus sign end cell equals cell 2 cross times 10 to the power of negative sign 3 end exponent M end cell row cell O H to the power of minus sign end cell equals cell square root of Kb cross times 0 comma 25 M end root end cell row cell 2 cross times 10 to the power of negative sign 3 end exponent M end cell equals cell square root of Kb cross times 0 comma 25 M end root end cell row Kb equals cell fraction numerator open parentheses 2 cross times 10 to the power of negative sign 3 end exponent M close parentheses squared over denominator 0 comma 25 M end fraction end cell row blank equals cell 1 comma 6 cross times 10 to the power of negative sign 5 end exponent M end cell end table end style 

Langkah berikutnya menentukan Kh garam begin mathsize 14px style H C O O N H subscript 4 end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell K subscript h end cell equals cell fraction numerator K subscript w over denominator K subscript a point K subscript b end fraction end cell row blank equals cell fraction numerator 10 to the power of negative sign 14 end exponent over denominator left parenthesis 6 comma 67 cross times 10 to the power of negative sign 5 end exponent right parenthesis cross times left parenthesis 1 comma 6 cross times 10 to the power of negative sign 5 end exponent right parenthesis end fraction end cell row blank equals cell 1 cross times 10 to the power of negative sign 4 end exponent end cell end table end style 

Derajat hidrolisis garam begin mathsize 14px style H C O O N H subscript 4 end style dapat dihitung dengan persamaan berikut:

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row h equals cell square root of K subscript h over M end root end cell row blank equals cell square root of fraction numerator 10 to the power of negative sign 4 end exponent over denominator 0 comma 15 M end fraction end root end cell row blank equals cell 0 comma 025 end cell row blank equals cell 2 comma 5 percent sign end cell end table end style 

Jadi, derajat hidrolisis larutan garam begin mathsize 14px style H C O O N H subscript 4 end style adalah 2,5%

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