Penambahan 5 ml larutan amonium klorida 0,5 M ke dalam 100 mL 0,5 M (), mengakibatkan .... (log 3,6 = 0,55 dan log 3 = 0,48)

Pertanyaan

Penambahan 5 ml larutan amonium klorida 0,5 M ke dalam 100 mL $begin mathsize 14px style N H subscript 4 O H end style$ 0,5 M ( $begin mathsize 14px style K subscript b equals 1 comma 8 cross times 10 to the power of negative sign 5 end exponent end style$ ), mengakibatkan ....
(log 3,6 = 0,55 dan log 3 = 0,48)

kenaikan pH sebesar 0,90 $space$
kenaikan pH sebesar 1,99 $space$
penurunan pH sebesar 0,92 $space$
penurunan pH sebesar 1,99 $space$
penurunan pH sebesar 2,09 $space$

Pembahasan Soal:

pH awal ditentukan oleh larutan basa lemah $begin mathsize 14px style N H subscript 4 O H end style$ .

$begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell open square brackets O H to the power of minus sign close square brackets end cell equals cell square root of K subscript b cross times M subscript b end root end cell row blank equals cell square root of 1 comma 8 cross times 10 to the power of negative sign 5 end exponent cross times 0 comma 5 end root end cell row blank equals cell square root of 0 comma 9 cross times 10 to the power of negative sign 5 end exponent end root end cell row blank equals cell square root of 9 cross times 10 to the power of negative sign 6 end exponent end root end cell row blank equals cell 3 cross times 10 to the power of negative sign 3 end exponent end cell row pOH equals cell negative sign log space open square brackets O H to the power of minus sign close square brackets end cell row blank equals cell negative sign log space 3 cross times 10 to the power of negative sign 3 end exponent end cell row blank equals cell 3 minus sign log space 3 end cell row blank equals cell 3 minus sign 0 comma 48 end cell row blank equals cell 2 comma 52 end cell row cell pH and pOH end cell equals 14 row pH equals cell 14 minus sign 2 comma 52 end cell row blank equals cell 11 comma 48 end cell end table end style$

Setelah ditambahkan garam $begin mathsize 14px style N H subscript 4 Cl end style$ akan membentuk larutan penyangga, maka pH ditentukan dengan:

$begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell open square brackets O H to the power of minus sign close square brackets end cell equals cell K subscript b cross times fraction numerator open square brackets N H subscript 4 O H close square brackets over denominator open square brackets N H subscript 4 Cl close square brackets end fraction end cell row blank equals cell 1 comma 8 cross times 10 to the power of negative sign 5 end exponent cross times fraction numerator fraction numerator 100 space mL cross times 0 comma 5 space M over denominator 105 space mL end fraction over denominator fraction numerator 5 space mL cross times 0 comma 5 space M over denominator 105 space mL end fraction end fraction end cell row blank equals cell 36 cross times 10 to the power of negative sign 5 end exponent end cell row blank equals cell 3 comma 6 cross times 10 to the power of negative sign 4 end exponent end cell row pOH equals cell negative sign log space open square brackets O H to the power of minus sign close square brackets end cell row blank equals cell negative sign log space 3 comma 6 cross times 10 to the power of negative sign 4 end exponent end cell row blank equals cell 4 minus sign log space 3 comma 6 end cell row blank equals cell 4 minus sign 0 comma 55 end cell row blank equals cell 3 comma 45 end cell row cell pH and pOH end cell equals 14 row pH equals cell 14 minus sign 3 comma 45 end cell row blank equals cell 10 comma 55 end cell end table end style$

pH menjadi turun, dari 11,48 menjadi 10,55 yaitu sebesar 0,93.

Jadi, jawaban yang benar adalah C.

Pembahasan terverifikasi oleh Roboguru

Terakhir diupdate 11 April 2021

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