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Jika 50 mL larutan 0,1 M ditambahkan 4,9 gram memiliki pH sebesar ...

Jika 50 mL larutan begin mathsize 14px style C H subscript 3 C O O H end style 0,1 M begin mathsize 14px style left parenthesis K subscript a equals 1 cross times 10 to the power of negative sign 5 end exponent right parenthesis end style ditambahkan 4,9 gram begin mathsize 14px style C H subscript 3 C O O K space left parenthesis M subscript r equals 98 space gram space mol to the power of negative sign 1 end exponent right parenthesis end style memiliki pH sebesar ...space  

  1. begin mathsize 14px style 6 minus sign log space 2 end style space 

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

  3. begin mathsize 14px style 5 minus sign log space 5 end style space 

  4. begin mathsize 14px style 6 end stylespace 

  5. begin mathsize 14px style 4 end stylespace 

Jawaban:

Pada reaksi kimia berikut:

begin mathsize 14px style C H subscript 3 C O O H left parenthesis italic a italic q right parenthesis equilibrium C H subscript 3 C O O to the power of minus sign left parenthesis italic a italic q right parenthesis plus H to the power of plus sign left parenthesis italic a italic q right parenthesis C H subscript 3 C O O K left parenthesis italic a italic q right parenthesis yields C H subscript 3 C O O 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 

Campuran asam lemah begin mathsize 14px style C H subscript 3 C O O H end style dan basa konjugasinya atau garamnya yaitu ion begin mathsize 14px style C H subscript 3 C O O to the power of minus sign end style membentuk larutan penyangga yang bersifat asam karena pada reaksi tersebut menghasilkan ion begin mathsize 14px style H to the power of plus sign end style.

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell H to the power of plus sign end cell equals cell K subscript a cross times fraction numerator mol space asam over denominator mol space garam end fraction end cell row cell H to the power of plus sign end cell equals cell K subscript a cross times fraction numerator mol space C H subscript 3 C O O H over denominator mol space C H subscript 3 C O O K end fraction end cell row cell H to the power of plus sign end cell equals cell K subscript a cross times fraction numerator V space C H subscript 3 C O O H cross times M space C H subscript 3 C O O H over denominator begin display style fraction numerator g space C H subscript 3 C O O K over denominator M subscript r space C H subscript 3 C O O K end fraction end style end fraction end cell row cell H to the power of plus sign end cell equals cell 1 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 M over denominator begin display style fraction numerator 4 comma 9 space gram over denominator 98 space g space mol to the power of negative sign 1 end exponent end fraction end style end fraction end cell row cell H to the power of plus sign end cell equals cell 10 to the power of negative sign 5 end exponent cross times fraction numerator 0 comma 005 space mol over denominator 0 comma 05 space mol end fraction end cell row cell H to the power of plus sign end cell equals cell 10 to the power of negative sign 6 end exponent space M 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 square brackets 10 to the power of negative sign 6 end exponent space M close square brackets end cell row pH equals 6 end table end style 

Jadi pH campuran tersebut adalah 6.

Oleh karena itu, jawaban yang benar adalah D.space 

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