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Sebanyak 50 mL larutan  0,1 M dicampur dengan 100 ...

Sebanyak 50 mL larutan begin mathsize 14px style H C N end style 0,1 M dicampur dengan 100 mL larutan begin mathsize 14px style Na C N end style 0,2 M. begin mathsize 14px style left parenthesis K subscript a equals 4 cross times 10 to the power of negative sign 5 end exponent right parenthesis end style untuk memperoleh larutan penyangga. pH campuran yang terjadi adalah...undefined 

  1. begin mathsize 14px style 5 minus sign log space 2 end style undefined 

  2. begin mathsize 14px style 5 end style undefined 

  3. begin mathsize 14px style 5 plus log space 2 end style undefined 

  4. begin mathsize 14px style 5 plus 2 space log space 2 end style undefined 

  5. begin mathsize 14px style 9 end style undefined 

Jawaban:

Larutan penyangga dapat terbentuk dari asam lemah dan basa konjugasinya atau basa lemah dan asam konjugasinya. Pada campuran di atas sudah ada komponen asam lemah dan basa konjugasinya dan larutan penyangga tersebut bersifat asam karena menghasilkan ion undefined dengan reaksi sebagai berikut.

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

begin mathsize 14px style 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 left square bracket asam space lemah right square bracket over denominator open square brackets garam close square brackets end fraction end cell 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 open square brackets H C N close square brackets over denominator open square brackets Na C N close square brackets end fraction end cell 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 mmol space H C N over denominator mmol space Na C N end fraction end cell 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 V space H C N cross times M space H C N over denominator V space Na C N cross times M space Na C N end fraction end cell row cell open square brackets H to the power of plus sign close square brackets end cell equals cell 4 cross times 10 to the power of negative sign 5 end exponent cross times fraction numerator 50 space mL cross times 0 comma 1 space mmol space mL to the power of negative sign 1 end exponent over denominator 100 space mL cross times 0 comma 2 space mmol space mL to the power of negative sign 1 end exponent end fraction end cell row cell open square brackets H to the power of plus sign close square brackets end cell equals cell 10 to the power of negative sign 5 end exponent space M 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 pH equals cell negative sign log open square brackets 10 to the power of negative sign 5 end exponent space M close square brackets end cell row pH equals 5 end table end style 

Jadi pH campuran adalah 5.

Oleh karena itu, jawaban yang benar adalah B.undefined  

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