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Darah mempunyai pH yang relatif tetap sekitar 7,4....

Darah mempunyai pH yang relatif tetap sekitar 7,4. Hal ini dimungkinkan karena adanya sistem penyangga H subscript 2 C O subscript 3 minus sign H C O subscript 3 to the power of minus sign sehingga meskipun setiap saat darah kemasukan berbagai zat yang bersifat asam maupun basa akan selalu dapat dinetralkan pengaruhnya terhadap perubahan pH. Bila darah kemasukan zat yang bersifat asam, maka ion H to the power of plus sign akan bereaksi dengan basa konjugasinya. Sebaliknya bila darah kemasukan zat yang bersifat basa maka ion O H to the power of minus sign akan bereaksi dengan asam lemahnya. Jika 100 mL darah mengandung H subscript 2 C O subscript 3 dan H C O subscript 3 to the power of minus sign, masing-masing 0,1 M, dengan K subscript a asam karbonat 8 cross times 10 to the power of negative sign 7 end exponent maka;

a. Tentukan pH darah

b. Berapakah pH darah jika ditambah 5 mL HCI 0,1 M

c. Berapakah pH darah jika ditambah 5 ml NaOH 0,1 M

Jawaban:

a. pH darah

table attributes columnalign right center left columnspacing 0px end attributes row cell n subscript H subscript 2 C O subscript 3 end subscript end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 cross times 100 end cell row blank equals cell 10 space mmol end cell row blank equals cell 0 comma 01 space mol end cell end table 

table attributes columnalign right center left columnspacing 0px end attributes row cell n subscript H C O subscript 3 to the power of minus sign end subscript end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 cross times 100 end cell row blank equals cell 10 space mmol end cell row blank equals cell 0 comma 01 space mol end cell end table 

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 n subscript H subscript 2 C O subscript 3 end subscript over n subscript H C O subscript 3 to the power of minus sign end subscript end cell row blank equals cell 8 cross times 10 to the power of negative sign 7 end exponent cross times fraction numerator 0 comma 01 over denominator 0 comma 01 end fraction end cell row blank equals cell 8 cross times 10 to the power of negative sign 7 end exponent space M end cell end table 

table attributes columnalign right center left columnspacing 0px end attributes row cell italic p H end cell 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 8 cross times 10 to the power of negative sign 7 end exponent end cell row blank equals cell 7 minus sign log space 8 end cell row blank equals cell 6 comma 09 end cell end table 

Maka pH darah adalah 6,09.

b. pH darah jika ditambah 5 mL HCI 0,1 M

table attributes columnalign right center left columnspacing 0px end attributes row cell n subscript HCl end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 cross times 5 end cell row blank equals cell 0 comma 5 space mmol end cell row blank equals cell 5 cross times 10 to the power of negative sign 4 end exponent space mol end cell end table 

Terjadi penambahan ion H to the power of plus sign sebesar Error converting from MathML to accessible text. 

Reaksi yang terjadi:

 

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 n subscript H subscript 2 C O subscript 3 end subscript over n subscript H C O subscript 3 to the power of minus sign end subscript end cell row blank equals cell 8 cross times 10 to the power of negative sign 7 end exponent cross times fraction numerator 0 comma 0105 over denominator 9 comma 5 cross times 10 to the power of negative sign 3 end exponent end fraction end cell row blank equals cell 8 comma 8 cross times 10 to the power of negative sign 7 end exponent space M end cell end table 

table attributes columnalign right center left columnspacing 0px end attributes row cell italic p H end cell 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 8 comma 8 cross times 10 to the power of negative sign 7 end exponent end cell row blank equals cell 7 minus sign log space 8 comma 8 end cell row blank equals cell 6 comma 06 end cell end table 

Maka pH darah setalah penambahan HCl adalah 6,06.

c. pH darah jika ditambah 5 ml NaOH 0,1 M

table attributes columnalign right center left columnspacing 0px end attributes row cell n subscript NaOH end cell equals cell M cross times V end cell row blank equals cell 0 comma 1 cross times 5 end cell row blank equals cell 0 comma 5 space mmol end cell row blank equals cell 5 cross times 10 to the power of negative sign 4 end exponent space mol end cell end table 

Terjadi penambahan ion O H to the power of minus sign sebesar Error converting from MathML to accessible text. 

Reaksi yang terjadi:

 

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 n subscript H subscript 2 C O subscript 3 end subscript over n subscript H C O subscript 3 to the power of minus sign end subscript end cell row blank equals cell 8 cross times 10 to the power of negative sign 7 end exponent cross times fraction numerator 9 comma 5 cross times 10 to the power of negative sign 3 end exponent over denominator 0 comma 0105 end fraction end cell row blank equals cell 7 comma 2 cross times 10 to the power of negative sign 7 end exponent space M end cell end table 

table attributes columnalign right center left columnspacing 0px end attributes row cell italic p H end cell 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 7 comma 2 cross times 10 to the power of negative sign 7 end exponent end cell row blank equals cell 7 minus sign log space 7 comma 2 end cell row blank equals cell 6 comma 14 end cell end table 

Maka pH darah setalah penambahan NaOH adalah 6,14.

Jadi, jawaban yang benar sesuai penjelasan diatas.

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