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Pada titrasi 25 mL larutan HCOOH 0,4 M dengan larutan 0,1 M. Tentukan: a. pH awal titrasi b. volume c. pH titik ekuivalen d. kurva titrasi

Pertanyaan

Pada titrasi 25 mL larutan HCOOH 0,4 M open parentheses K subscript a equals 1 middle dot 10 to the power of negative sign 5 end exponent close parentheses dengan larutan Ca open parentheses O H close parentheses subscript 2 0,1 M. Tentukan:

a. pH awal titrasi

b. volume Ca open parentheses O H close parentheses subscript 2

c. pH titik ekuivalen

d. kurva titrasispace

Pembahasan Soal:

a. pH awal titrasi merupakan pH awal asam lemah HCOOH, yaitu 2,69, dengan perhitungan sebagai berikut:

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 square root of K subscript a cross times open square brackets H C O O H close square brackets end root end cell row cell open square brackets H to the power of plus sign close square brackets end cell equals cell square root of 1 cross times 10 to the power of negative sign 5 end exponent cross times 0 comma 4 end root end cell row cell open square brackets H to the power of plus sign close square brackets end cell equals cell square root of 4 cross times 10 to the power of negative sign 6 end exponent end root end cell row cell open square brackets H to the power of plus sign close square brackets end cell equals cell 2 cross times 10 to the power of negative sign 3 end exponent end cell row pH equals cell negative sign log space open square brackets H to the power of plus sign close square brackets end cell row pH equals cell negative sign log space open parentheses 2 cross times 10 to the power of negative sign 3 end exponent close parentheses end cell row bold pH bold equals cell bold 2 bold comma bold 69 end cell end table


b. Volume basa yang dibutuhkan adalah 50 mL, dengan perhitungan sebagai berikut.

table attributes columnalign right center left columnspacing 0px end attributes row cell V subscript a cross times M subscript a cross times valensi space asam end cell equals cell V subscript b cross times M subscript b cross times valensi space basa end cell row cell 25 cross times 0 comma 4 cross times 1 end cell equals cell V subscript b cross times 0 comma 1 cross times 2 end cell row cell V subscript b end cell equals cell fraction numerator 10 over denominator 0 comma 2 end fraction end cell row cell V subscript italic b end cell bold equals cell bold 50 bold space bold mL end cell end table


c. pH pada titik ekuivalen dihitung dengan rumus garam terhidrolisis bersifat basa, yaitu 9,06, dengan perhitungan sebagai berikut.

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 square root of K subscript w over K subscript a cross times open square brackets H C O O to the power of minus sign close square brackets end root end cell row cell open square brackets O H to the power of minus sign close square brackets end cell equals cell square root of fraction numerator 10 to the power of negative sign 14 end exponent over denominator 1 cross times 10 to the power of negative sign 5 end exponent end fraction cross times open parentheses bevelled fraction numerator 10 space mmol over denominator 75 space mL end fraction close parentheses end root end cell row cell open square brackets O H to the power of minus sign close square brackets end cell equals cell square root of 10 to the power of negative sign 9 end exponent cross times 0 comma 133 end root end cell row cell open square brackets O H to the power of minus sign close square brackets end cell equals cell 1 comma 15 cross times 10 to the power of negative sign 5 end exponent space M end cell 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 pOH equals cell 4 comma 94 end cell row pH equals cell 14 minus sign pOH end cell row pH equals cell 14 minus sign 4 comma 94 end cell row bold pH bold equals cell bold 9 bold comma bold 06 end cell end table


d. Kurva titrasi

space

Pembahasan terverifikasi oleh Roboguru

Terakhir diupdate 04 Mei 2021

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