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Magnesium nitrit yang mengandung 0,32 g atom oksigen direaksikan dengan 45 mL asam nitrit 0,2 M. Jika ke dalam sistem tersebut ditambahkan 1 mL  1 M. Berapakah pH sebelum dan sesudah penambahan asam. (, , ; )

Pertanyaan

Magnesium nitrit yang mengandung 0,32 g atom oksigen direaksikan dengan 45 mL asam nitrit 0,2 M. Jika ke dalam sistem tersebut ditambahkan 1 mL H Cl 1 M. Berapakah pH sebelum dan sesudah penambahan asam.

(A subscript r space O equals 16Mg equals 24N equals 14K subscript a equals 4 comma 5 cross times 10 to the power of negative sign 4 end exponent)

Pembahasan Soal:

table attributes columnalign right center left columnspacing 0px end attributes row cell m space O end cell equals cell fraction numerator indeks space O cross times A subscript r space O over denominator M subscript r space Mg open parentheses N O subscript 2 close parentheses subscript 2 end fraction cross times m space Mg open parentheses N O subscript 2 close parentheses subscript 2 end cell row cell 0 comma 32 space g end cell equals cell fraction numerator 4 cross times 16 over denominator 116 end fraction cross times m space Mg open parentheses N O subscript 2 close parentheses subscript 2 end cell row cell m space Mg open parentheses N O subscript 2 close parentheses subscript 2 end cell equals cell 0 comma 58 space g end cell end table 

table attributes columnalign right center left columnspacing 0px end attributes row cell n space Mg open parentheses N O subscript 2 close parentheses subscript 2 end cell equals cell m over M subscript r end cell row blank equals cell fraction numerator 0 comma 58 over denominator 116 end fraction end cell row blank equals cell 0 comma 005 space mol end cell row blank equals cell 5 space mmol end cell end table 


table attributes columnalign right center left columnspacing 0px end attributes row cell n space H N O subscript 2 end cell equals cell V cross times M end cell row blank equals cell 45 space mL cross times 0 comma 2 space M end cell row blank equals cell 9 space mmol end cell end table 


pH sebelum penambahan 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 N O subscript 2 close square brackets over denominator 2 cross times left square bracket Mg open parentheses N O subscript 2 close parentheses subscript 2 right square bracket end fraction end cell row blank equals cell 4 comma 5 cross times 10 to the power of negative sign 4 end exponent cross times fraction numerator 9 space mmol over denominator 2 cross times 5 space mmol end fraction end cell row blank equals cell 4 comma 05 cross times 10 to the power of negative sign 4 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 4 comma 05 cross times 10 to the power of negative sign 4 end exponent right parenthesis end cell row blank equals cell 4 minus sign log space 4 comma 05 end cell end table 


pH setelah penambahan asam:

table attributes columnalign right center left columnspacing 0px end attributes row cell n space H Cl end cell equals cell V cross times M end cell row blank equals cell 1 space mL cross times 1 space M end cell row blank equals cell 1 space mmol end cell end table 

Asam yang ditambahkan akan dinetralkan oleh basa konjugasinya, yaitu magnesium nitrit.

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 N O subscript 2 close square brackets over denominator 2 cross times left square bracket Mg open parentheses N O subscript 2 close parentheses subscript 2 right square bracket end fraction end cell row blank equals cell 4 comma 5 cross times 10 to the power of negative sign 4 end exponent cross times fraction numerator 10 space mmol over denominator 2 cross times 4 comma 5 space mmol end fraction end cell row blank equals cell 5 cross times 10 to the power of negative sign 4 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 5 cross times 10 to the power of negative sign 4 end exponent right parenthesis end cell row blank equals cell 4 minus sign log space 5 end cell end table 


Jadi, pH sebelum penambahan asam sebesar 4 - log 4,05 dan pH setelah penambahan asam sebesar 4 - log 5.

Pembahasan terverifikasi oleh Roboguru

Terakhir diupdate 20 Mei 2021

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