# ocr chemistry acid question

Healthy blood at a pH of 7.40 has a hydrogencarbonate : carbonic acid ratio of 10.5 : 1.
A patient is admitted to hospital. The patient’s blood pH is measured as 7.20.
Calculate the hydrogencarbonate : carbonic acid ratio in the patient’s blood.

q 4dii

I don't underrstand the last part of this question, how did they get the ratio and rearranged it?
(edited 5 years ago)
Original post by chem222
Healthy blood at a pH of 7.40 has a hydrogencarbonate : carbonic acid ratio of 10.5 : 1.
A patient is admitted to hospital. The patient’s blood pH is measured as 7.20.
Calculate the hydrogencarbonate : carbonic acid ratio in the patient’s blood.

q 4dii

I don't underrstand the last part of this question, how did they get the ratio and rearranged it?

This is a buffers question.

ka = [H+][A-]/[HA]

if you are given pH you can work out [H+]
If you are given ka you can work out ratio of [A-] to [HA]
Original post by charco
This is a buffers question.

ka = [H+][A-]/[HA]

if you are given pH you can work out [H+]
If you are given ka you can work out ratio of [A-] to [HA]

How do you rearrange it at the end?
I got
4.18 x 10^-7 = 6.31 x 10-8 x HCO3- / H2CO3

not sure how to rearrange this...
Original post by chem222
How do you rearrange it at the end?
I got
4.18 x 10^-7 = 6.31 x 10-8 x HCO3- / H2CO3

not sure how to rearrange this...

Calculate the hydrogencarbonate : carbonic acid ratio in the patient’s blood.

Well, you have it on the RHS, just move everything else to the LHS
Original post by chem222
how do you rearrange it at the end?
I got
4.18 x 10^-7 = 6.31 x 10-8 x hco3- / h2co3

not sure how to rearrange this...

[hco3-] = 4.18 x 10^-7. = 6.62
[h2co3]. 6.31 x 10^-8 1