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Pertanyaan

Sebanyak 25 mL larutan begin mathsize 14px style H Cl end style dititrasi dengan larutan NaOH 0,1 M menggunakan indikator BTB. Setelah tercapai titik ekuivalen yang ditandai timbulnya warna biru, memerlukan larutan begin mathsize 14px style Na O H end style sebanyak 25 mL.

  1. Hitunglah konsentrasi molaritas begin mathsize 14px style H Cl end style!
  2. Hitung pH larutan pada saat:Volume begin mathsize 14px style Na O H end style belum dicampurkan atau diteteskan.
    1. Volume begin mathsize 14px style Na O H end style yang dicampurkan atau diteteskan sebanyak 5 mL.
    2. Volume begin mathsize 14px style Na O H end style yang dicampurkan atau diteteskan sebanyak 20 mL
    3. Volume begin mathsize 14px style Na O H end style yang dicampurkan atau diteteskan sebanyak 26 mL
    4. Volume begin mathsize 14px style Na O H end style yang dicampurkan atau diteteskan sebanyak 30 mL
  3. Buatlah kurva titrasi volume begin mathsize 14px style Na O H end style dengan pH dari perhitungan 2.1, 2.2, 2.3, 2.4, dan 2.5.

S. Hidayati

Master Teacher

Mahasiswa/Alumni Universitas Indonesia

Jawaban terverifikasi

Jawaban

jawaban yang tepat dapat dilihat pada perhitungan di atas.

Pembahasan

Molaritas larutan begin mathsize 14px style H Cl end style:

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell a cross times V subscript HCl cross times M subscript HCl end cell equals cell b cross times V subscript NaOH cross times M subscript NaOH end cell row cell 1 cross times 25 space mL cross times M subscript HCl end cell equals cell 1 cross times 25 space mL cross times 0 comma 1 space M end cell row cell M subscript HCl end cell equals cell fraction numerator 1 cross times 25 space mL cross times 0 comma 1 space M over denominator 1 cross times 25 space mL end fraction end cell row cell M subscript HCl end cell equals cell 0 comma 1 space M end cell end table end style 
 

Titrasi ini merupakan titrasi asam kuat dan basa kuat. Mol larutan begin mathsize 14px style H Cl end style yang digunakan dalam titrasi, yaitu:

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell n space H Cl end cell equals cell V cross times M end cell row blank equals cell 25 space mL cross times 0 comma 1 space M end cell row blank equals cell 2 comma 5 space mmol end cell end table end style 

Reaksi titrasi: begin mathsize 14px style Na O H and H Cl yields Na Cl and H subscript 2 O end style 

Perbandingan koefisien begin mathsize 14px style H Cl end style dan begin mathsize 14px style Na O H end style sebesar 1 : 1, berarti perbandingan jumlah mol kedua zat saat mencapai titik ekuivalen sebesar 1 :1.


pH larutan saat belum dicampurkan begin mathsize 14px style Na O H end style:

Pada keadaan ini, pH larutan hanya ditentukan dari larutan begin mathsize 14px style H Cl end style.

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell open square brackets H to the power of plus sign close square brackets end cell equals cell a cross times M space H Cl end cell row blank equals cell 1 cross times left parenthesis 10 to the power of negative sign 1 end exponent right parenthesis end cell row blank equals cell 10 to the power of negative sign 1 end exponent space M end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row pH equals cell negative sign log space open square brackets H to the power of plus sign close square brackets end cell row blank equals cell negative sign log space left parenthesis 10 to the power of negative sign 1 end exponent right parenthesis end cell row blank equals 1 end table end style 

pH larutan saat belum dicampurkan begin mathsize 14px style Na O H end style sebanyak 5 mL:

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell n space Na O H end cell equals cell V cross times M end cell row blank equals cell 5 space mL cross times 0 comma 1 space M end cell row blank equals cell 0 comma 5 space mmol end cell end table end style 

Mol begin mathsize 14px style H Cl end style lebih besar daripada mol begin mathsize 14px style Na O H end style yang ditambahkan sehingga begin mathsize 14px style Na O H end style sebagai pereaksi pembatas (habis bereaksi).

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell open square brackets H to the power of plus sign close square brackets end cell equals cell a cross times M space H Cl end cell row blank equals cell 1 cross times fraction numerator n space H Cl over denominator V space total end fraction end cell row blank equals cell 1 cross times fraction numerator 2 comma 0 space mmol over denominator 25 plus space 5 space mL end fraction end cell row blank equals cell 6 comma 67 cross times 10 to the power of negative sign 2 end exponent end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row pH equals cell negative sign log space open square brackets H to the power of plus sign close square brackets end cell row blank equals cell negative sign log space left parenthesis 6 comma 67 cross times 10 to the power of negative sign 2 end exponent right parenthesis end cell row blank equals cell 2 minus sign log space 6 comma 67 end cell row blank equals cell 1 comma 18 end cell end table end style 

pH larutan saat belum dicampurkan begin mathsize 14px style Na O H end style sebanyak 20 mL:

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell n space Na O H end cell equals cell V cross times M end cell row blank equals cell 20 space mL cross times 0 comma 1 space M end cell row blank equals cell 2 comma 0 space mmol end cell end table end style 

Mol begin mathsize 14px style H Cl end style lebih besar daripada mol begin mathsize 14px style Na O H end style yang ditambahkan sehingga begin mathsize 14px style Na O H end style sebagai pereaksi pembatas (habis bereaksi).

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell open square brackets H to the power of plus sign close square brackets end cell equals cell a cross times M space H Cl end cell row blank equals cell 1 cross times fraction numerator n space H Cl over denominator V space total end fraction end cell row blank equals cell 1 cross times fraction numerator 0 comma 5 space mmol over denominator 25 plus 20 space mL end fraction end cell row blank equals cell 1 comma 11 cross times 10 to the power of negative sign 2 end exponent end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row pH equals cell negative sign log space open square brackets H to the power of plus sign close square brackets end cell row blank equals cell negative sign log space left parenthesis 1 comma 11 cross times 10 to the power of negative sign 2 end exponent right parenthesis end cell row blank equals cell 2 minus sign log space 1 comma 11 end cell row blank equals cell 1 comma 95 end cell end table end style 

pH larutan saat belum dicampurkan begin mathsize 14px style Na O H end style sebanyak 26 mL:

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell n space Na O H end cell equals cell V cross times M end cell row blank equals cell 26 space mL cross times 0 comma 1 space M end cell row blank equals cell 2 comma 6 space mmol end cell end table end style 

Mol begin mathsize 14px style Na O H end style lebih besar daripada mol begin mathsize 14px style H Cl end style yang ditambahkan sehingga begin mathsize 14px style H Cl end style sebagai pereaksi pembatas (habis bereaksi).

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 b cross times M space Na O H end cell row blank equals cell 1 cross times fraction numerator n space Na O H over denominator V space total end fraction end cell row blank equals cell 1 cross times fraction numerator 0 comma 1 space mmol over denominator 25 plus 26 space mL end fraction end cell row blank equals cell 1 comma 96 cross times 10 to the power of negative sign 3 end exponent end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes 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 left parenthesis 1 comma 96 cross times 10 to the power of negative sign 3 end exponent right parenthesis end cell row blank equals cell 3 minus sign log space 1 comma 96 end cell row blank equals cell 2 comma 71 end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row pH equals cell 14 minus sign pOH end cell row blank equals cell 14 minus sign 2 comma 71 end cell row blank equals cell 11 comma 29 end cell end table end style 

pH larutan saat belum dicampurkan begin mathsize 14px style Na O H end style sebanyak 30 mL:

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell n space Na O H end cell equals cell V cross times M end cell row blank equals cell 30 space mL cross times 0 comma 1 space M end cell row blank equals cell 3 comma 0 space mmol end cell end table end style 

Mol begin mathsize 14px style Na O H end style lebih besar daripada mol begin mathsize 14px style H Cl end style yang ditambahkan sehingga begin mathsize 14px style H Cl end style sebagai pereaksi pembatas (habis bereaksi).

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 b cross times M space Na O H end cell row blank equals cell 1 cross times fraction numerator n space Na O H over denominator V space total end fraction end cell row blank equals cell 1 cross times fraction numerator 0 comma 5 space mmol over denominator 25 plus 30 space mL end fraction end cell row blank equals cell 9 comma 09 cross times 10 to the power of negative sign 3 end exponent end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes 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 left parenthesis 9 comma 09 cross times 10 to the power of negative sign 3 end exponent right parenthesis end cell row blank equals cell 3 minus sign log space 9 comma 09 end cell row blank equals cell 2 comma 04 end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row pH equals cell 14 minus sign pOH end cell row blank equals cell 14 minus sign 2 comma 04 end cell row blank equals cell 11 comma 96 end cell end table end style 


Kurva titrasi:

Saat ekuivalen, pH larutan sebesar 7 ikut dimasukkan ke dalam data sehingga kurva titrasi yang diperoleh sebagai berikut.


Jadi, jawaban yang tepat dapat dilihat pada perhitungan di atas.

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