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Sebanyak 8 gram kristal  dilarutkan dalam 1 liter ...

Sebanyak 8 gram kristal Na O H dilarutkan dalam 1 liter larutan H C N 0,3 M. Bila K subscript a equals 2 cross times 10 to the power of negative sign 5 end exponent dan A subscript r space Na equals 23, maka besarnya pH campuran adalah ....space 

  1. 5 - log 2space 

  2. 5space 

  3. 6 - log 2space 

  4. 9 + log 2space 

  5. 10space 

Jawaban:

Reaksi: Na O H and H C N yields Na C N and H subscript 2 O 

table attributes columnalign right center left columnspacing 0px end attributes row cell n space Na O H end cell equals cell m over M subscript r end cell row blank equals cell fraction numerator 8 space g over denominator 40 space g forward slash mol end fraction end cell row blank equals cell 0 comma 2 space mol end cell end table 

table attributes columnalign right center left columnspacing 0px end attributes row cell n space H C N end cell equals cell V cross times M end cell row blank equals cell 1 space L cross times 0 comma 3 space M end cell row blank equals cell 0 comma 3 space mol end cell end table 

Pereaksi pembatasnya adalah Na O H, maka:

Campuran membentuk larutan penyangga asam.

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 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 blank equals cell 2 cross times 10 to the power of negative sign 5 end exponent cross times fraction numerator begin display style bevelled fraction numerator 0 comma 1 space mol over denominator 1 space L end fraction end style over denominator begin display style bevelled fraction numerator 0 comma 2 space mol over denominator 1 space L end fraction end style end fraction end cell row blank equals cell 1 cross times 10 to the power of negative sign 5 end exponent end cell end table 

table attributes columnalign right center left columnspacing 0px end attributes row pH equals cell negative sign log space open square brackets H to the power of plus sign close square brackets end cell row blank equals cell negative sign log space left parenthesis 1 cross times 10 to the power of negative sign 5 end exponent right parenthesis end cell row blank equals 5 end table 


Jadi, jawaban yang tepat adalah B.

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