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400 mL larutan begin mathsize 14px style C H subscript 3 C O O H end style 0,1 M direaksikan dengan 100 mL larutan begin mathsize 14px style Ca open parentheses O H close parentheses subscript 2 end style 0,1 M. Tentukan: (begin mathsize 14px style K subscript a equals 10 to the power of negative sign 5 end exponent end style)

a. pH larutan

b. pH larutan jika ditambahkan 0,001 mol HCl

c. pH larutan jika ditambahkan 0,001 mol NaOH

d. pH larutan jika diencerkan dengan menambahkan 100 mL air

I. Solichah

Master Teacher

Jawaban terverifikasi

Jawaban

jawaban yang benar sesuai penjelasan diatas.

Pembahasan

a. pH larutan

Menentukan mol larutan:

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell n subscript C H subscript 3 C O O H end subscript end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 cross times 400 end cell row blank equals cell 40 space mmol end cell row blank equals cell 0 comma 04 space mol end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell n subscript Ca open parentheses O H close parentheses subscript 2 end subscript end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 cross times 100 end cell row blank equals cell 10 space mmol end cell row blank equals cell 0 comma 01 space mol end cell end table end style 

Reaksi yang terjadi:

 

Menentukan pH larutan:

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 K subscript a cross times n subscript asam over n subscript garam end cell row blank equals cell 10 to the power of negative sign 5 end exponent cross times fraction numerator 0 comma 02 over denominator 0 comma 01 end fraction end cell row blank equals cell 2 cross times 10 to the power of negative sign 5 end exponent end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell italic p H end cell 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 2 cross times 10 to the power of negative sign 5 end exponent end cell row blank equals cell 5 minus sign log space 2 end cell row blank equals cell 4 comma 7 end cell end table end style 

Maka, pH larutan adalah 4,7.

b. pH larutan jika ditambahkan 0,001 mol HCl

Reaksi yang terjadi:

 

Menentukan pH larutan:

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 K subscript a cross times n subscript asam over n subscript garam end cell row blank equals cell 10 to the power of negative sign 5 end exponent cross times fraction numerator 0 comma 021 over denominator 0 comma 009 end fraction end cell row blank equals cell 2 comma 3 cross times 10 to the power of negative sign 5 end exponent end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell italic p H end cell 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 2 comma 3 cross times 10 to the power of negative sign 5 end exponent end cell row blank equals cell 5 minus sign log space 2 comma 3 end cell row blank equals cell 4 comma 6 end cell end table end style 

Maka, pH larutan setelah ditambahkan HCl adalah 4,7.

c. pH larutan jika ditambahkan 0,001 mol NaOH

Reaksi yang terjadi:

 

Menentukan pH larutan:

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 K subscript a cross times n subscript asam over n subscript garam end cell row blank equals cell 10 to the power of negative sign 5 end exponent cross times fraction numerator 0 comma 019 over denominator 0 comma 011 end fraction end cell row blank equals cell 1 comma 7 cross times 10 to the power of negative sign 5 end exponent end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell italic p H end cell 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 1 comma 7 cross times 10 to the power of negative sign 5 end exponent end cell row blank equals cell 5 minus sign log space 1 comma 7 end cell row blank equals cell 4 comma 8 end cell end table end style 

Maka, pH larutan setelah ditambahkan NaOH adalah 4,8.

d. pH larutan jika diencerkan dengan menambahkan 100 mL air

Menentukan konsentrasi larutan setelah penambahan 100 mL air:

 begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell open square brackets C H subscript 3 C O O H close square brackets end cell equals cell n over V subscript total end cell row blank equals cell fraction numerator 0 comma 02 over denominator 500 plus 100 end fraction end cell row blank equals cell fraction numerator 0 comma 02 over denominator 600 end fraction end cell row blank equals cell 3 comma 3 cross times 10 to the power of negative sign 5 end exponent space mmol end cell row blank equals cell 3 comma 3 cross times 10 to the power of negative sign 8 end exponent space mol end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell left square bracket open parentheses C H subscript 3 C O O close parentheses subscript 2 Ca right square bracket end cell equals cell n over V subscript total end cell row blank equals cell fraction numerator 0 comma 01 over denominator 500 plus 100 end fraction end cell row blank equals cell fraction numerator 0 comma 01 over denominator 600 end fraction end cell row blank equals cell 1 comma 7 cross times 10 to the power of negative sign 5 end exponent space mmol end cell row blank equals cell 1 comma 7 cross times 10 to the power of negative sign 8 end exponent space mol end cell end table end style 

Menentukan pH larutan:

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 K subscript a cross times fraction numerator open square brackets C H subscript 3 C O O H close square brackets over denominator open square brackets open parentheses C H subscript 3 C O O close parentheses subscript 2 Ca close square brackets end fraction end cell row blank equals cell 10 to the power of negative sign 5 end exponent cross times fraction numerator 3 comma 3 cross times 10 to the power of negative sign 8 end exponent over denominator 1 comma 7 cross times 10 to the power of negative sign 8 end exponent end fraction end cell row blank equals cell 1 comma 9 cross times 10 to the power of negative sign 5 end exponent end cell end table end style 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell italic p H end cell 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 1 comma 9 cross times 10 to the power of negative sign 5 end exponent end cell row blank equals cell 5 minus sign log space 1 comma 9 end cell row blank equals cell 4 comma 7 end cell end table end style 

Maka, pH larutan setelah pengenceran adalah 4,7.

Jadi, jawaban yang benar sesuai penjelasan diatas.

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