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± Composition of Inorganic Conjugate Acid-Base Pairs in Blood pH of blood The tw

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Question

± Composition of Inorganic Conjugate Acid-Base Pairs in Blood

pH of blood

The two most important inorganic blood buffers (acid-base conjugate pairs) are the phosphoric acid and carbonic acid systems. The pH of normal blood is 7.40.

Part A

At a pH of 7.40, what is the ratio of the molar concentrations of PO43 to HPO42?

Express your answer using two significant figures.

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Part B

At a pH of 7.40, what is the ratio of the molar concentrations of HPO42 to H2PO4?

Express your answer using two significant figures.

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Part C

At a pH of 7.40, what is the ratio of the molar concentrations of H2PO4 to H3PO4?

Express your answer using two significant figures.

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Part D

At a pH of 7.40, what is the ratio of the molar concentrations of CO32 to HCO3?

Express your answer using two significant figures.

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Part E

At a pH of 7.40, what is the ratio of the molar concentrations of HCO3 to H2CO3?

Express your answer using two significant figures.

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Part F

Which conjugate acid-base pair is most responsible for maintaining the pH of blood?

Which conjugate acid-base pair is most responsible for maintaining the  of blood?

[CO32][HCO3]

[HCO3][H2CO3]

[H2PO4][H3PO4]

[PO43][HPO42]

[HPO42][H2PO4]

± Composition of Inorganic Conjugate Acid-Base Pairs in Blood

The following table gives the acid-dissociation constant values, Ka, for carbonic acid, H2CO3, and phosphoric acid, H3PO4. Acid Ka1 Ka2 Ka3 H2CO3 4.3×107 5.6×1011 not applicable H3PO4 7.2×103 6.2×108 4.2×1013

pH of blood

The two most important inorganic blood buffers (acid-base conjugate pairs) are the phosphoric acid and carbonic acid systems. The pH of normal blood is 7.40.

Part A

At a pH of 7.40, what is the ratio of the molar concentrations of PO43 to HPO42?

Express your answer using two significant figures.

[PO43][HPO42] =

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Part B

At a pH of 7.40, what is the ratio of the molar concentrations of HPO42 to H2PO4?

Express your answer using two significant figures.

[HPO42][H2PO4] =

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Part C

At a pH of 7.40, what is the ratio of the molar concentrations of H2PO4 to H3PO4?

Express your answer using two significant figures.

[H2PO4][H3PO4] =

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Part D

At a pH of 7.40, what is the ratio of the molar concentrations of CO32 to HCO3?

Express your answer using two significant figures.

[CO32][HCO3] =

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Part E

At a pH of 7.40, what is the ratio of the molar concentrations of HCO3 to H2CO3?

Express your answer using two significant figures.

[HCO3][H2CO3] =

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Part F

Normal metabolic processes produce significant amounts of acid, sometimes up to 10 mol/day, in the human body. Thus it is desirable that the buffer system for blood contain more conjugate base than acid.

Which conjugate acid-base pair is most responsible for maintaining the pH of blood?

Normal metabolic processes produce significant amounts of acid, sometimes up to 10 , in the human body. Thus it is desirable that the buffer system for blood contain more conjugate base than acid.

Which conjugate acid-base pair is most responsible for maintaining the  of blood?

[CO32][HCO3]

[HCO3][H2CO3]

[H2PO4][H3PO4]

[PO43][HPO42]

[HPO42][H2PO4]

Explanation / Answer

Part-A

PH   = PKa + log[PO43-]/[HPO42-]

Pka = -logKa

        = -log4.2*10-13

       = 12.3767

PH   = PKa + log[PO43-]/[HPO42-]

7.4 =12.3767 + log[PO43-]/[HPO42-]

7.4-12.3767 = log[PO43-]/[HPO42-]

log[PO43-]/[HPO42-] = -4.9767

[PO43-]/[HPO42-]     = 10-4.9767   = 1.05*10-5

Part-B

     PH   = PKa + log[HPO42-]/[H2PO4-]

     PKa = -logKa

               = -log6.2*10-8

                = 7.207

7.4   = 7.207 + log[PO43-]/[HPO4-]

7.4-7.207 = log[HPO42-]/[H2PO4-]

log[HPO42-]/[H2PO4-] = 0.193

[HPO42-]/[H2PO4-]     = 100.193    = 1.6

part-C

PH   = Pka + log[H2PO4-]/[H3PO4]

PKa = -logKa

       = -log7.2*10-3

       = 2.1426

PH   = Pka + log[H2PO4-]/[H3PO4]

7.4 = 2.1426 + log[H2PO4-]/[H3PO4]

log[H2PO4-]/[H3PO4] = 7.4-2.1426

log[H2PO4-]/[H3PO4]   = 5.2574

[H2PO4-]/[H3PO4]    = 105.2574

[H2PO4-]/[H3PO4] = 180883/1

Part-D

PH   = Pka + log[CO32-]/[HCO3-]

Pka = -logKa

       = -log5.6*10-11

        = 10.2518

PH   = Pka + log[CO32-]/[HCO3-]

7.4 = 10.2518+ log[CO32-]/[HCO3-]

log[CO32-]/[HCO3-] = 7.4-10.2518

log[CO32-]/[HCO3-]      = -2.8518

[CO32-]/[HCO3-]    = 10-2.8518

[CO32-]/[HCO3-]   = 0.0014

part-e

PH   = PKa + log[HCO3-]/[H2CO3]

PKa = -logKa

      = -log4.3*10-7

      = 6.3665

PH   = PKa + log[HCO3-]/[H2CO3]

7.4 = 6.3665 + log[HCO3-]/[H2CO3]

log[HCO3-]/[H2CO3] = 7.4-6.3665

log[HCO3-]/[H2CO3]   = 1.0335

[HCO3-]/[H2CO3]   = 101.0335

[HCO3-]/[H2CO3]     = 10.80