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Jika diketahui . Tentukan harga pH dari campuran berikut: 100 mL larutan 0,2 M + 100 mL HCl 0,1 M

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:

100 mL larutan begin mathsize 14px style N H subscript 3 end style 0,2 M + 100 mL HCl 0,1 M

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

100 mL larutan begin mathsize 14px style N H subscript 3 end style 0,2 M 

100 mL HCl 0,1 M

Ditanya: pH ...?

Jawab:

mol begin mathsize 14px style N H subscript 3 end style = 100 mL x 0,2 M = 20 mmol

mol HCl = 100 mL x 0,1 M = 10 mmol

reaksi

begin mathsize 14px style 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 10 space mmol over denominator 10 space mmol 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 space end exponent end style

pOH = - log begin mathsize 14px style open square brackets O H to the power of minus sign close square brackets end style

pOH = - log begin mathsize 14px style 10 to the power of negative sign 5 end exponent end style

pOH = 5

pH = 14 - pOH

pH = 14 - 5

pH = 9

Jadi, pH larutan tersebut adalah 9.

Pembahasan terverifikasi oleh Roboguru

Terakhir diupdate 18 Mei 2021

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