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Hitung pH larutan dari larutan

Pertanyaan

Hitung pH larutan dari larutan begin mathsize 14px style Na C N space 0 comma 1 space M space left parenthesis K subscript a space H C N equals 4 cross times 10 to the power of negative sign 6 end exponent right parenthesis end stylespace 

Pembahasan Soal:

Garam yang berasal dari asam lemah dan basa kuat akan terionisasi sempurna dalam air menghasilkan kation dan anion. Anion berasal dari asam lemah dan kation dari basa kuat seperti reaksi berikut.

begin mathsize 14px style Na C N left parenthesis italic a italic q right parenthesis yields with plus air on top C N to the power of minus sign left parenthesis italic a italic q right parenthesis plus Na to the power of plus sign left parenthesis italic a italic q right parenthesis end style 

Anion dari asam lemah begin mathsize 14px style C N to the power of minus sign end style akan bereaksi dengan air (terhidrolisis) sesuai dengan persamaan reaksi berikut.

begin mathsize 14px style C N to the power of minus sign left parenthesis italic a italic q right parenthesis plus H subscript 2 O left parenthesis italic a italic q right parenthesis equilibrium H C N left parenthesis italic a italic q right parenthesis plus O H to the power of minus sign left parenthesis italic a italic q right parenthesis end style 

Adanya ion undefined dalam hasil reaksi menunjukkan bahwa larutan garam tersebut bersifat 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 square root of K subscript italic w over K subscript italic a cross times open square brackets anion close square brackets subscript garam 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 4 cross times 10 to the power of negative sign 6 end exponent end fraction cross times 10 to the power of negative sign 1 end exponent 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 58 cross times 10 to the power of negative sign 5 end exponent space M end cell row blank blank blank row pOH equals cell negative sign log open square brackets O H to the power of minus sign close square brackets end cell row pOH equals cell negative sign log left square bracket 1 comma 58 cross times 10 to the power of negative sign 5 end exponent right square bracket end cell row pOH equals cell 5 minus sign log space 1 comma 58 end cell row blank blank blank row pH equals cell 14 minus sign pOH end cell row pH equals cell 14 minus sign left parenthesis 5 minus sign log space 1 comma 58 right parenthesis end cell row pH equals cell 9 plus log space 1 comma 58 end cell row blank blank blank end table end style 

Jadi pH NaCN adalah begin mathsize 14px style bold 9 bold plus bold log bold space bold 1 bold comma bold 58 end style.undefined 

Pembahasan terverifikasi oleh Roboguru

Terakhir diupdate 01 April 2021

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