Tentukan pH 100 mL larutan 0,2 M bila terionisasi 10%!

Pertanyaan

Tentukan pH 100 mL larutan $C H subscript 3 C O O H$ 0,2 M bila terionisasi 10%! $space$

Pembahasan Soal:

Agar dapat menentukan nilai pH larutan $C H subscript 3 C O O H$ tersebut, maka perlu dicari terlebih dahulu nilai tetapan kesetimbangan asam atau $K subscript a$ dari nilai derajat ionisasi $open parentheses alpha close parentheses$ dengan cara sebagai berikut: $space$

$table attributes columnalign right center left columnspacing 0px end attributes row alpha equals cell square root of K subscript a over M end root end cell row cell 10 over 100 end cell equals cell square root of fraction numerator K subscript a over denominator 0 comma 2 end fraction end root end cell row cell open parentheses 10 to the power of negative sign 1 end exponent close parentheses squared end cell equals cell open parentheses square root of fraction numerator K subscript a over denominator 2 middle dot 10 to the power of negative sign 1 end exponent end fraction end root close parentheses squared end cell row cell 10 to the power of negative sign 2 end exponent end cell equals cell fraction numerator K subscript a over denominator 2 middle dot 10 to the power of negative sign 1 end exponent end fraction end cell row cell K subscript a end cell equals cell 10 to the power of negative sign 2 end exponent cross times 2 middle dot 10 to the power of negative sign 1 end exponent end cell row cell K subscript a end cell equals cell 2 cross times 10 to the power of negative sign 3 end exponent end cell end table$

Setelah diketahui nilai $K subscript a$ , maka nilai pH larutan dapat dihitung dengan cara sebagai berikut. $space$

$table attributes columnalign right center left columnspacing 0px end attributes row cell open square brackets H to the power of plus sign close square brackets end cell equals cell square root of K subscript a cross times M end root end cell row cell open square brackets H to the power of plus sign close square brackets end cell equals cell square root of 2 middle dot 10 to the power of negative sign 3 end exponent cross times 2 middle dot 10 to the power of negative sign 1 end exponent end root end cell row cell open square brackets H to the power of plus sign close square brackets end cell equals cell square root of 4 cross times 10 to the power of negative sign 4 end exponent end root end cell row cell open square brackets H to the power of plus sign close square brackets end cell equals cell 2 cross times 10 to the power of negative sign 2 end exponent end cell row blank blank blank row pH equals cell negative sign log space open square brackets H to the power of plus sign close square brackets end cell row pH equals cell negative sign log space 2 cross times 10 to the power of negative sign 2 end exponent end cell row pH equals cell 2 minus sign log space 2 end cell end table$

Jadi, pH larutan tersebut adalah 2 - log 2. $space$

Pembahasan terverifikasi oleh Roboguru

Terakhir diupdate 05 Mei 2021

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