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Jika diketahui . Tentukan harga pH dari campuran berikut: 50 mL larutan 0,1 M + 100 mL

Pertanyaan

Jika diketahui 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 harga pH dari campuran berikut:

50 mL larutan begin mathsize 14px style N H subscript 4 O H end style 0,1 M + 100 mL begin mathsize 14px style open parentheses N H subscript 4 close parentheses subscript 2 S O subscript 4 space 0 comma 2 space M end style

Pembahasan Soal:

Diketahui:

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

50 mL larutan begin mathsize 14px style N H subscript 4 O H end style 0,1 M

100 mL begin mathsize 14px style open parentheses N H subscript 4 close parentheses subscript 2 S O subscript 4 space 0 comma 2 space M end style

Ditanya: pH ....?

Jawab:

mol begin mathsize 14px style N H subscript 4 O H end style = 50 mL x 0,1 M = 5 mmol

mol begin mathsize 14px style open parentheses N H subscript 4 close parentheses subscript 2 S O subscript 4 end style = 100 mL x 0,2 M = 20 mmol

open square brackets O H to the power of minus sign close square brackets equals K subscript b space end subscript cross times fraction numerator mol space basa over denominator mol space asam space konjugasi end fraction open square brackets O H to the power of minus sign close square brackets equals 10 to the power of negative sign 5 end exponent cross times fraction numerator 5 space mmol over denominator 20 space mmol space x space 2 end fraction open square brackets O H to the power of minus sign close square brackets equals 1 comma 25 space cross times 10 to the power of negative sign 6 end exponent   

pOH = - log undefined

pOH = - log left square bracket 1 comma 25 space cross times 10 to the power of negative sign 6 end exponent right square bracket  

pOH = 6 - log 1,25

pOH = 6 - 0,1 

pOH = 5,9

pH = 14 - pOH

pH = 14 - 5,9

pH = 8,1

Jadi, pH larutan tersebut adalah 8,1.

 

Pembahasan terverifikasi oleh Roboguru

Terakhir diupdate 18 Mei 2021

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