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Sebanyak 100 mL larutan mengandung HCOOH dan HCOONa masing-masing 0,1 M, (Ka= ). a. Hitung pH larutan awal b. Hitung pH setelah ditambah 1 mL HCI 0,1 M (tulis reaksi yang terjadi) c. Hitung pH setelah ditambah 1 mL NaOH 0,1 M (tulis reaksi yang terjadi)

Pertanyaan

Sebanyak 100 mL larutan mengandung HCOOH dan HCOONa masing-masing 0,1 M, (Ka= begin mathsize 14px style 10 to the power of negative sign 5 end exponent end style).
a. Hitung pH larutan awal
b. Hitung pH setelah ditambah 1 mL HCI 0,1 M (tulis reaksi yang terjadi)
c. Hitung pH setelah ditambah 1 mL NaOH 0,1 M (tulis reaksi yang terjadi)

Pembahasan Soal:

a. pH larutan awal: mol HCOOH(as.lemah)=100mLbegin mathsize 14px style cross times end style0,1M=10mmol, mol HCOONa(garam)=100mLbegin mathsize 14px style cross times end style0,1M=10mmol.
 

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 Ka cross times fraction numerator mol space As point lemah over denominator mol space garam end fraction end cell row blank equals cell 10 to the power of negative sign 5 end exponent cross times fraction numerator 10 mmol over denominator 10 mmol end fraction end cell row blank equals cell 10 to the power of negative sign 5 end exponent end cell row pH equals cell negative sign log open square brackets H to the power of plus sign close square brackets end cell row blank equals cell negative sign log space 10 to the power of negative sign 5 end exponent end cell row blank equals 5 end table end style
 

b. Penambahan 1mL HCL 0,1M, mol HCl=0,1mmol. HCl akan bereaksi dengan Garam(basa):
 


 

dengan demikian maka pH larutan penyangga menjadi:
 

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 Ka cross times fraction numerator mol space As point lemah over denominator mol space garam end fraction end cell row blank equals cell 10 to the power of negative sign 5 end exponent cross times fraction numerator 10 comma 1 mmol over denominator 9 comma 9 mmol end fraction end cell row blank equals cell 1 comma 01 middle dot 10 to the power of negative sign 5 end exponent end cell row pH equals cell negative sign log open square brackets H to the power of plus sign close square brackets end cell row blank equals cell negative sign log space 1 comma 01 middle dot 10 to the power of negative sign 5 end exponent end cell row blank equals cell 5 minus sign log space 1 comma 01 end cell end table end style
 

c. Penambahan 1mL NaOH 0,1M, mol NaOH=0,1mmol. NaOH akan bereaksi dengan HCOOH(As.lemah):
 


 

Dengan demikian maka pH larutan penyangga menjadi:space
 

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 Ka cross times fraction numerator mol space As point lemah over denominator mol space garam end fraction end cell row blank equals cell 10 to the power of negative sign 5 end exponent cross times fraction numerator 9 comma 9 mmol over denominator 10 comma 1 mmol end fraction end cell row blank equals cell 0 comma 98 middle dot 10 to the power of negative sign 5 end exponent equals 9 comma 8 middle dot 10 to the power of negative sign 6 end exponent end cell row pH equals cell negative sign log open square brackets H to the power of plus sign close square brackets end cell row blank equals cell negative sign log space 9 comma 8 middle dot 10 to the power of negative sign 6 end exponent end cell row blank equals cell 6 minus sign log space 9 comma 8 end cell end table end style

Pembahasan terverifikasi oleh Roboguru

Terakhir diupdate 04 April 2021

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