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Larutan CH3​COOH mempunyai pH=2 , jika diencerkan hingga 100 kali kemudian sebanyak 100 ml larutan tersebut direaksikan dengan 100 ml NaOH 0,01 M. Berapakah pH setelah pengenceran dan setelah penambahan ?

Pertanyaan

Larutan C H subscript 3 C O O H mempunyai pH=2 , jika diencerkan hingga 100 kali kemudian sebanyak 100 ml larutan tersebut direaksikan dengan 100 ml Na O H 0,01 M. Berapakah pH setelah pengenceran dan setelah penambahan Na O H?

N. Puspita

Master Teacher

Jawaban terverifikasi

Pembahasan

Asam merupakan zat yang dapat melepaskan ion H to the power of plus sign, sedangkan basa merupakan zat yang dapat melepaskan ion O H to the power of minus sign. Larutan C H subscript 3 C O O H spacetermasuk asam lemah, dan Na O H termasuk basa kuat. Ketika asam lemah direaksikan dengan basa kuat, kemudian yang tersisa adalah asam lemah maka akan terbentuk garam berupa larutan penyangga.

  • Molaritas asam asetat sebelum pengenceran:

table attributes columnalign right center left columnspacing 0px end attributes row pH equals 2 row cell left square bracket H plus right square bracket end cell equals cell 10 to the power of negative sign 2 end exponent end cell row cell asumsi space Ka end cell equals cell 10 to the power of negative sign 5 end exponent end cell row blank blank blank row cell M subscript italic a end cell equals cell left square bracket H plus right square bracket squared over K subscript a end cell row blank equals cell left parenthesis 10 to the power of negative sign 2 end exponent right parenthesis squared over 10 to the power of negative sign 5 end exponent end cell row blank equals cell 10 space M end cell row blank blank blank end table 

  • pH asam asetat setelah pengenceran

table attributes columnalign right center left columnspacing 0px end attributes row cell Molaritas space setelah space pengenceran end cell equals cell fraction numerator M subscript 1 over denominator faktor space pengenceran end fraction end cell row blank equals cell fraction numerator 10 space M over denominator 100 end fraction end cell row blank equals cell 10 to the power of negative sign 1 end exponent end cell row blank blank blank row cell open square brackets H to the power of plus sign close square brackets end cell equals cell square root of K subscript a cross times M subscript a end root end cell row blank equals cell square root of 10 to the power of negative sign 5 end exponent cross times 10 to the power of negative sign 3 end exponent end root end cell row blank equals cell square root of 10 to the power of negative sign 8 end exponent end root end cell row blank equals cell 10 to the power of negative sign 4 end exponent end cell row blank blank blank 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 4 end exponent end cell row blank equals 4 end table 

  • Menghitung mol C H subscript 3 C O O H dan Na O H.

n space C H subscript 3 C O O H space equals MxV space space space space space space space space space space space space space space space space space space space space space equals 0 comma 1 space Mx 100 space mL space space space space space space space space space space space space space space space space space space space space space equals space 10 space mmol n space Na O H space space space space space space space space equals MxV space space space space space space space space space space space space space space space space space space space space space equals 0 comma 01 space Mx 100 space mL space space space space space space space space space space space space space space space space space space space space space equals space 1 space mmol

  • pH setelah dicampurkan Na O H.

 

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 italic a cross times fraction numerator mol space asam space 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 space mmol over denominator 1 space mmol end fraction end cell row blank equals cell 9 cross times 10 to the power of negative sign 5 end exponent end cell row blank blank blank 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 9 cross times 10 to the power of negative sign 5 end exponent end cell row blank equals cell 5 minus sign log space 9 end cell end table 

 

Jadi, pH setelah pengenceran adalah 4 dan setelah penambahan Na O H adalah 5-log 9.

 

 

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