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Sebanyak 100 mL  0,1 M dicampur dengan 100 mL laru...

Sebanyak 100 mL begin mathsize 14px style H subscript 2 S O subscript 4 end style 0,1 M dicampur dengan 100 mL larutan begin mathsize 14px style N H subscript 3 end style 0,2 M. Jika begin mathsize 14px style K subscript italic b space N H subscript 3 equals 1 cross times 10 to the power of negative sign 5 end exponent end style, pH campuran yang terbentuk adalah ....

  1. 5-log 2space 

  2. 5+log 1space 

  3. 5+log 2space 

  4. 5,5+log 5space 

  5. 6,5-log 1space 

Jawaban:

Campuran dari kedua larutan tersebut akan membentuk garam asam karena mol ekivalen basa lemah sama dengan mol ekivalen asam kuat. 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell H subscript 2 S O subscript 4 and 2 N H subscript 3 end cell rightwards arrow cell open parentheses N H subscript 4 close parentheses subscript 2 S O subscript 4 end cell row blank blank blank row cell mol space ek space H subscript 2 S O subscript 4 end cell equals cell M cross times V cross times valensi end cell row blank equals cell 0 comma 1 cross times 100 cross times 2 end cell row blank equals cell 20 space mmol end cell row blank blank blank row cell mol space ek space N H subscript 3 end cell equals cell M cross times V cross times valensi end cell row blank equals cell 0 comma 2 cross times 100 cross times 1 end cell row blank equals cell 20 space mmol end cell row blank blank blank row cell mol space open parentheses N H subscript 4 close parentheses subscript 2 S O subscript 4 end subscript end cell equals cell 20 space mmol end cell row blank blank blank row cell Mol space ek space N H subscript 4 to the power of plus end cell equals cell valensi cross times mol space garam end cell row blank equals cell 2 cross times 20 space mmol end cell row blank equals cell 40 space mmol end cell row blank blank blank row cell left square bracket N H subscript 4 to the power of plus right square bracket end cell equals cell fraction numerator mol over denominator V space campuran end fraction end cell row blank equals cell fraction numerator 40 space mmol over denominator 200 space mL end fraction end cell row blank equals cell 0 comma 2 space M end cell row blank blank blank row cell open square brackets H to the power of plus sign close square brackets end cell equals cell square root of K subscript italic w over K subscript italic b cross times open square brackets garam close square brackets end root end cell row blank equals cell square root of 10 to the power of negative sign 14 end exponent over 10 to the power of negative sign 5 end exponent cross times 2 cross times 10 to the power of negative sign 1 end exponent end root end cell row blank equals cell square root of 2 cross times 10 end root to the power of negative sign 10 end exponent end cell row blank equals cell 1 comma 47 cross times 10 to the power of negative sign 5 end exponent 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 blank equals cell negative sign log space 1 comma 47 cross times 10 to the power of negative sign 5 end exponent end cell row blank equals cell 5 minus sign log space 1 comma 4 end cell row blank blank blank end table end style 


Jadi, jawaban yang mendekati adalah A.

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