Question

The pH of blood is 7.35. It is maintained in part by the buffer system composed of carbonic acid (H2CO3) and the bicarbonate (hydrogen carbonate, HCO3-) ion.What is the ratio of [bicarbonate]/[carbonic acid] at this pH? For carbonic acid, Ka1 = 4.2 10-7.A) [bicarbonate]/[carbonic acid] = 0.11D) [bicarbonate]/[carbonic acid] = 9.4B) [bicarbonate]/[carbonic acid] = 0.38E) None of the above ratios is correct.C) [bicarbonate]/[carbonic acid] = 2.65

Answer 1

Answer: Option (B) is the correct answer.

Step-by-step explanation:

The given data is as follows.

pH for blood = 7.35,

For carbonic acid,
`K_{a_(1)} = 4.2 * 10^(-7)`

Therefore, calculate the pH of buffer solution as follows.

pH =
`pK_{a_(1)} + log \frac{\text{Conjugate anion}}{\text{Acid}}`

=
`-log K_{a_(1)} + log \frac{\text{bicarbonate}}{\text{carbonic acid}}`

Now, putting the given values into the above formula as follows.

pH =
`-log K_{a_(1)} + log \frac{\text{bicarbonate}}{\text{carbonic acid}}`

7.35 =
`-log (4.2 * 10^(-7)) + log \frac{\text{bicarbonate}}{\text{carbonic acid}}`

7.35 =
`6.377 + log \frac{\text{bicarbonate}}{\text{carbonic acid}}`

`\frac{\text{bicarbonate}}{\text{carbonic acid}} = 10^(0.937)`

= 9.4

Therefore, we can conclude that the ratio of [bicarbonate]/[carbonic acid] at this pH is 9.4.