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Tentukan pH 250 mL larutan yang mengandung 0,98 gram .

Pertanyaan

Tentukan pH 250 mL larutan yang mengandung 0,98 gram begin mathsize 14px style Na C N space left parenthesis K subscript a equals 5 cross times 10 to the power of negative sign 10 end exponent comma space Mr equals 51 space gram space mol to the power of negative sign 1 end exponent right parenthesis end style.undefined 

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 Na C N close square brackets end cell equals cell fraction numerator italic g space Na C N over denominator M subscript r space Na C N end fraction cross times fraction numerator 1000 over denominator V space larutan end fraction end cell row cell open square brackets Na C N close square brackets end cell equals cell fraction numerator 0 comma 98 space gram over denominator 51 space gram space mol to the power of negative sign 1 end exponent end fraction cross times fraction numerator 1000 over denominator 250 space mL end fraction end cell row cell open square brackets Na C N close square brackets end cell equals cell 7 comma 7 cross times 10 to the power of negative sign 2 end exponent space M space comma space kosentrasi space Na C N space sama space dengan space C N to the power of minus sign end cell row blank blank blank 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 x space open square brackets C N 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 5 cross times 10 to the power of negative sign 10 end exponent end fraction cross times 7 comma 7 cross times 10 to the power of negative sign 2 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 24 cross times 10 to the power of negative sign 3 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 24 cross times 10 to the power of negative sign 3 end exponent right square bracket end cell row pOH equals cell 3 minus sign log space 1 comma 24 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 3 minus sign log space 1 comma 24 right parenthesis end cell row pH equals cell 11 plus log space 1 comma 24 end cell end table end style  

Jadi pH NaCN adalah begin mathsize 14px style bold 11 bold plus bold log bold space bold 1 bold comma bold 24 end style.undefined 

Pembahasan terverifikasi oleh Roboguru

Terakhir diupdate 01 April 2021

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