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Jika 250 mL larutan 0,1 M dicampuran dengan 750 mL larutan 0,1 M, . a. Tentukan pH campuran! b. Hitung pH larutan jika dalam campuran tersebut ditambah 5 mL HCl 0,1 M! c. Hitung pH larutan jika d

Jika 250 mL larutan begin mathsize 14px style N H subscript 4 O H end style 0,1 M dicampuran dengan 750 mL larutan begin mathsize 14px style N H subscript 4 Cl end style 0,1 M, begin mathsize 14px style K subscript b space N H subscript 4 O H equals 1 comma 8 cross times 10 to the power of negative sign 5 end exponent end style.

a. Tentukan pH campuran!

b. Hitung pH larutan jika dalam campuran tersebut ditambah 5 mL HCl 0,1 M!

c. Hitung pH larutan jika dalam campuran tersebut ditambah 5 mL NaOH 0,1 M!

Jawaban:

a. Tentukan pH campuran!

Menentukan nilai mol larutan:

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell n subscript N H subscript 4 O H end subscript end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 cross times 250 end cell row blank equals cell 25 space mmol end cell row blank equals cell 0 comma 025 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 N H subscript 4 Cl end subscript end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 cross times 750 end cell row blank equals cell 75 space mmol end cell row blank equals cell 0 comma 075 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 O H to the power of minus sign close square brackets end cell equals cell K subscript b cross times n subscript N H subscript 4 O H end subscript over n subscript N H subscript 4 to the power of plus end subscript end cell row blank equals cell 1 comma 8 cross times 10 to the power of negative sign 5 end exponent cross times fraction numerator 0 comma 025 over denominator 0 comma 075 end fraction end cell row blank equals cell 0 comma 6 cross times 10 to the power of negative sign 5 end exponent end cell row blank equals cell 6 cross times 10 to the power of negative sign 6 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 O H end cell equals cell negative sign space log space open square brackets O H to the power of minus sign close square brackets end cell row blank equals cell negative sign space log space 6 cross times 10 to the power of negative sign 6 end exponent end cell row blank equals cell 6 space minus sign space log space 6 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 14 space minus sign space log space italic p O H end cell row blank equals cell 14 space minus sign space left parenthesis 6 space minus sign log space 6 right parenthesis end cell row blank equals cell 8 plus log space 6 end cell row blank equals cell 8 comma 78 end cell end table end style 

Jadi, pH campuran adalah 8,78.

b. Hitung pH larutan jika dalam campuran tersebut ditambah 5 mL HCl 0,1 M!

Menentukan nilai mol:

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell n subscript HCl end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 cross times 5 end cell row blank equals cell 0 comma 5 space mmol end cell row blank equals cell 0 comma 0005 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 O H to the power of minus sign close square brackets end cell equals cell K subscript b cross times n subscript N H subscript 4 O H end subscript over n subscript N H subscript 4 to the power of plus end subscript end cell row blank equals cell 1 comma 8 cross times 10 to the power of negative sign 5 end exponent cross times fraction numerator 0 comma 0245 over denominator 0 comma 0755 end fraction end cell row blank equals cell 5 comma 8 cross times 10 to the power of negative sign 6 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 O H end cell equals cell negative sign space log space open square brackets O H to the power of minus sign close square brackets end cell row blank equals cell negative sign space log space 5 comma 8 cross times 10 to the power of negative sign 6 end exponent end cell row blank equals cell 6 space minus sign space log space 5 comma 8 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 14 space minus sign space log space italic p O H end cell row blank equals cell 14 space minus sign space left parenthesis 6 space minus sign log space 5 comma 8 right parenthesis end cell row blank equals cell 8 plus log space 5 comma 8 end cell row blank equals cell 8 comma 76 end cell end table end style  

Jadi, pH larutan setelah penambahan HCl adalah 8,76.

c. Hitung pH larutan jika dalam campuran tersebut ditambah 5 mL NaOH 0,1 M!

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell n subscript NaOH end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 cross times 5 end cell row blank equals cell 0 comma 5 space mmol end cell row blank equals cell 0 comma 0005 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 O H to the power of minus sign close square brackets end cell equals cell K subscript b cross times n subscript N H subscript 4 O H end subscript over n subscript N H subscript 4 to the power of plus end subscript end cell row blank equals cell 1 comma 8 cross times 10 to the power of negative sign 5 end exponent cross times fraction numerator 0 comma 0255 over denominator 0 comma 0745 end fraction end cell row blank equals cell 6 comma 2 cross times 10 to the power of negative sign 6 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 O H end cell equals cell negative sign space log space open square brackets O H to the power of minus sign close square brackets end cell row blank equals cell negative sign space log space 6 comma 2 cross times 10 to the power of negative sign 6 end exponent end cell row blank equals cell 6 space minus sign space log space 6 comma 2 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 14 space minus sign space log space italic p O H end cell row blank equals cell 14 space minus sign space left parenthesis 6 space minus sign log space 6 comma 2 right parenthesis end cell row blank equals cell 8 plus log space 6 comma 2 end cell row blank equals cell 8 comma 79 end cell end table end style 

Jadi, pH larutan setelah penambahan NaOH adalah 8,79.

Jadi, jawaban yang benar sesuai penjelasan diatas.

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