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

50 mL $begin mathsize 14px style space N H subscript 4 O H space 0 comma 1 space M end style$ 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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