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50 mL dicampur dengan 100 mL  0,2 M. Jika , tentuk...

50 mLbegin mathsize 14px style space N H subscript 4 O H space 0 comma 1 space M end style dicampur dengan 100 mL begin mathsize 14px style open parentheses N H subscript 4 close parentheses subscript 2 S O subscript 4 end subscript end style 0,2 M. Jika begin mathsize 14px style K subscript b space N H subscript 4 O H equals 10 to the power of negative sign 5 end exponent end style, tentukan pH campuran tersebut!

Jawaban:

Campuran kedua larutan diatas merupakan campuran larutan penyangga karena terdiri atas larutan basa lemah dengan garamnya yang menghasilkan sifat basa.

Penentuan mol begin mathsize 14px style N H subscript 4 O H space dan space open parentheses N H subscript 4 close parentheses subscript 2 S O subscript 4 end subscript end style:


begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell mol space N H subscript 4 O H end cell equals cell 50 space mL cross times 0 comma 1 space M end cell row blank equals cell 5 space mmol end cell row cell mol space open parentheses N H subscript 4 close parentheses subscript 2 S O subscript 4 end cell equals cell 100 space mL cross times 0 comma 2 space M end cell row blank equals cell 20 space mmol end cell end table end style 


Garam begin mathsize 14px style open parentheses N H subscript 4 close parentheses subscript 2 S O subscript 4 end subscript end style memiliki 2 valensi, karena memiliki 2 kation basa begin mathsize 14px style N H subscript 4 to the power of plus end style. pH yang dihasilkan memiliki sifat basa.


begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell open square brackets O H to the power of minus sign close square brackets end cell equals cell K subscript b cross times fraction numerator mol space basa over denominator mol space garam cross times valensi end fraction end cell row blank equals cell 10 to the power of negative sign 5 end exponent cross times fraction numerator 5 space mmol over denominator 20 space mmol cross times 2 end fraction end cell row blank equals cell 1 comma 25 cross times 10 to the power of negative sign 6 end exponent end cell row pOH equals cell negative sign log space open square brackets O H to the power of minus sign close square brackets end cell row blank equals cell negative sign log space 1 comma 25 cross times 10 to the power of negative sign 6 end exponent end cell row blank equals cell 6 minus sign log space 1 comma 25 end cell row pH equals cell 14 minus sign left parenthesis 6 minus sign log space 1 comma 25 right parenthesis end cell row blank equals cell 8 plus log space 1 comma 25 end cell end table end style


Jadi, pH campuran larutan penyangga yang dihasilkan adalah begin mathsize 14px style 8 plus log space 1 comma 25 end style.

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