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Di dalam 500 mL larutan terdapat 4,1 gram  yang te...

Di dalam 500 mL larutan terdapat 4,1 gram begin mathsize 14px style C H subscript 3 C O O Na end style yang terlarut. Jika nilai begin mathsize 14px style Ka space C H subscript 3 C O O H equals 10 to the power of negative sign 5 end exponent end style dan Ar Na=23, C=12, O=16,maka pH larutan tersebut adalah...undefined 

  1. 3undefined 

  2. 4undefined 

  3. 5undefined 

  4. 9undefined 

  5. 10undefined 

Jawaban:

Pertama, mencari konsentrasi larutan begin mathsize 14px style C H subscript 3 C O O Na end style
 

begin mathsize 14px style Mr space C H subscript 3 C O O Na equals left parenthesis 2 cross times Ar space C right parenthesis plus left parenthesis 3 cross times Ar space H right parenthesis plus left parenthesis 2 cross times Ar space O right parenthesis plus left parenthesis Ar space Na right parenthesis Mr space C H subscript 3 C O O Na equals left parenthesis 2 cross times 12 right parenthesis plus left parenthesis 3 cross times 1 right parenthesis plus left parenthesis 2 cross times 16 right parenthesis plus 23 equals 82 space begin inline style bevelled g over mol end style  M equals fraction numerator bevelled Massa over Mr over denominator bevelled Volume over 1000 end fraction equals fraction numerator bevelled fraction numerator 4 comma 1 space over denominator 82 end fraction over denominator bevelled 500 over 1000 end fraction equals 0 comma 1 space M end style 
 

Kedua, menghitung nilai pH garam terhidrolisis.
 

begin mathsize 14px style open square brackets O H to the power of minus sign close square brackets equals square root of K subscript w over K subscript a cross times open square brackets Garam close square brackets end root open square brackets O H to the power of minus sign close square brackets equals 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 10 to the power of negative sign 1 end exponent end root equals 10 to the power of negative sign 5 end exponent pOH equals minus sign log space open square brackets O H to the power of minus sign close square brackets equals minus sign log space 10 to the power of negative sign 5 end exponent equals 5 pH equals 14 minus sign pOH equals 14 minus sign 5 equals 9 end style 
 

Jadi, jawaban yang paling tepat adalah D. 

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