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Pertanyaan

Gelas kimia I berisi 100 mL larutan CH3COOH 0,1 M. Gelas kimia II berisi 100 mL larutan NaOH 0,1 M. Jika Ka CH3COOH = 10-5

a. Tentukan pH larutan pada gelas kimia I
b. Tentukan pH larutan pada gelas kimia II
c. Jika larutan pada gelas kimia I dicampurkan dengan gelas kimia II, tentukan pH campurannya!

I. Nur

Master Teacher

Mahasiswa/Alumni Universitas Negeri Malang

Jawaban terverifikasi

Pembahasan

a. pH larutan pada gelas kimia I

    Pada gelas kimia I terdapat asam lemah. Berikut perhitungan mencari pH dari asam lemah.

    begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell left square bracket straight H to the power of plus right square bracket equals square root of straight K subscript straight a cross times straight M subscript straight a end root equals square root of 10 to the power of negative 5 end exponent cross times 0 comma 1 end root equals square root of 10 to the power of negative 6 end exponent end root equals 10 to the power of negative 3 end exponent end cell end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank space end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank space end table  table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell pH equals negative log space left square bracket straight H to the power of plus right square bracket equals negative log space 10 to the power of negative 3 end exponent equals 3 end cell end table end style   


b. pH larutan pada gelas kimia II

    Pada gelas kimia I terdapat basa kuat. Berikut perhitungan mencari pH dari basa kuat.


    begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell open square brackets OH to the power of minus close square brackets equals straight b cross times straight M subscript straight b equals 1 cross times 0 comma 1 equals 10 to the power of negative 1 end exponent end cell row blank blank blank row blank blank cell pOH equals negative log space open square brackets OH to the power of minus close square brackets equals negative log space 10 to the power of negative 1 end exponent equals 1 end cell row blank blank blank row blank blank cell pH equals 14 minus pOH equals 14 minus 1 equals 13 end cell end table end style 


c. pH campuran

    Berikut adalah stoikiometri reaksi yang terjadi:


 


    Karena asam lemah dan basa kuat habis bereaksi maka akan terbentuk garam basa, dimana garam tersebut akan mengalami reaksi hidrolisis sebagian.
 

    begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell left square bracket OH to the power of minus right square bracket equals square root of straight K subscript straight w over straight K subscript straight a cross times left square bracket CH subscript 3 COO to the power of minus right square bracket end root equals square root of 10 to the power of negative 14 end exponent over 10 to the power of negative 5 end exponent cross times fraction numerator 10 space mmol over denominator 200 space mL end fraction end root equals square root of 5 cross times 10 to the power of negative 11 end exponent end root equals 2 comma 24 cross times 10 to the power of negative 5 comma 5 end exponent end cell end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank space end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank space end table  table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell pOH equals negative log space left square bracket OH to the power of minus right square bracket equals negative log space 2 comma 24 cross times 10 to the power of negative 5 comma 5 end exponent equals 5 comma 5 minus log space 2 comma 24 equals 5 comma 5 minus 0 comma 35 equals 5 comma 15 end cell end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank space end table table attributes columnalign right center left columnspacing 0px end attributes row blank blank space end table  table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell pH equals 14 minus pOH equals 14 minus 5 comma 15 equals 8 comma 85 end cell end table end style  


Jadi, pH larutan pada gelas kimia I sebesar 3; pH larutan pada gelas kimia II sebesar 13; dan pH campuran sebesar 8,85.space 

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