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Larutan penyangga sebanyak 1 L mengandung  0,1 M d...

Larutan penyangga sebanyak 1 L mengandung begin mathsize 14px style N H subscript 3 end style 0,1 M dan begin mathsize 14px style N H subscript 4 Cl end style 0,1 M. Jika diketahui Kb begin mathsize 14px style N H subscript 3 end stylebegin mathsize 14px style 1 comma 8 cross times 10 to the power of negative sign 5 end exponent end style, maka tentukan:

  1. pH larutan penyangga
  2. pH larutan penyangga jika ditambah akuades sebanyak 19 L

Jawaban:

1. pH larutan penyangga

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell mol space N H subscript 3 end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 space M cross times 1 space L end cell row blank equals cell 0 comma 1 space mol end cell end table end style


begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell mol space N H subscript 4 Cl end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 space M cross times 1 space L end cell row blank equals cell 0 comma 1 space mol end cell end table end style

mol konjugasi dari basa lemah pada garam begin mathsize 14px style N H subscript 4 Cl end style




pH pada larutan penyangga basa:


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 Kb cross times begin inline style b over g end style end cell row blank equals cell 1 cross times 10 to the power of negative sign 5 end exponent cross times begin inline style fraction numerator 0 comma 1 over denominator 0 comma 1 end fraction end style end cell row blank equals cell 10 to the power of negative sign 5 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 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 10 to the power of negative sign 5 end exponent end cell row blank equals 5 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 5 end cell row blank equals 9 end table end style


2. pH larutan setelah ditambah 19 L air.

mol begin mathsize 14px style N H subscript 3 end style dan undefined setelah penambahan 19 L air (Volume total= (1+19)L= 20 L)


begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell mol space N H subscript 3 end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 space M cross times 20 space L end cell row blank equals cell 2 space mol end cell end table end style


begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell mol space N H subscript 4 Cl end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 space M cross times 20 space L end cell row blank equals cell 2 space mol end cell end table end style
 

mol konjugasi dari basa lemah pada garam begin mathsize 14px style N H subscript 4 Cl end style



pH pada larutan penyangga basa:


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 Kb cross times begin inline style b over g end style end cell row blank equals cell 1 cross times 10 to the power of negative sign 5 end exponent cross times begin inline style 2 over 2 end style end cell row blank equals cell 10 to the power of negative sign 5 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 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 10 to the power of negative sign 5 end exponent end cell row blank equals 5 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 5 end cell row blank equals 9 end table end style

 

Jadi, pH larutan penyangga sebelum diencerkan dan sesudah diencerkan adalah 9.

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