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Hitunglah pH NaOH sebanyak 0,4 gram yang dilarutkan dalam 1000 mL air. ()

Pertanyaan

Hitunglah pH NaOH sebanyak 0,4 gram yang dilarutkan dalam 1000 mL air.

(begin mathsize 14px style Ar space Na equals 23 comma space O equals 16 comma space H equals 1 end style)

Pembahasan Soal:

NaOH adalah senyawa basa kuat. Penentuan kekuatan basa dihitung berdasarkan nilai begin mathsize 14px style open square brackets O H to the power of minus sign close square brackets end style.

  • Hitung konsentrasi molar NaOH.

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell italic M space Na O H end cell equals cell m over Mr cross times 1000 over V end cell row cell italic M space Na O H end cell equals cell fraction numerator 0 comma 4 over denominator 40 end fraction cross times 1000 over 1000 end cell row cell italic M space Na O H end cell equals cell 0 comma 01 space M end cell end table end style 

  • Hitung valensi basa (b) berdasarkan reaksi ionisasi NaOH.

begin mathsize 14px style Na O H yields Na to the power of plus sign and O H to the power of minus sign space left parenthesis b equals 1 right parenthesis end style 

  • Hitung begin mathsize 14px style open square brackets O H to the power of minus sign close square brackets end style

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell open square brackets O H to the power of minus sign close square brackets end cell equals cell b cross times M subscript b end cell row cell open square brackets O H to the power of minus sign close square brackets end cell equals cell 1 cross times 0 comma 01 space M end cell row cell open square brackets O H to the power of minus sign close square brackets end cell equals cell 1 cross times 10 to the power of negative sign 2 end exponent end cell end table end style 

  • Hitung pOH dan pH.

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row pOH equals cell negative sign log space open square brackets O H to the power of minus sign close square brackets end cell row pOH equals cell negative sign log space 1 cross times 10 to the power of negative sign 2 end exponent end cell row pOH equals cell 2 minus sign log space 1 end cell row pOH equals cell 2 minus sign 0 end cell row pOH equals 2 row blank blank blank row pH equals cell 14 minus sign pOH end cell row pH equals cell 14 minus sign 2 end cell row pH equals 12 end table end style 


Jadi, pH NaOH adalah 12.

 

Pembahasan terverifikasi oleh Roboguru

Terakhir diupdate 12 Maret 2021

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