Question

Following intense exercise, the blood pH was determined to be 7.1. If the HCO3- is 7.5mM and the pKa for HCO3- is 6.1, what is the CO2 concentration in the blood

Answer 1

`0.75\ \text{mM}`

Step-by-step explanation:

Concentration of
`HCO_3^-` =
`[HCO_3^-]=7.5\ \text{mM}`

`pK_a` for
`HCO_3^-` = 6.1

`pH` of blood = 7.1

The reaction is as follows

`H_2CO_3+H_2O\rightarrow HCO_3^-+H_3O^+`

From the Henderson equation we get

`pH=pK_a+\log([HCO_3^-])/([H_2CO_3])\\\Rightarrow 7.1=6.1+\log (7.5)/([H_2CO_3])\\\Rightarrow 1=\log(7.5)/([H_2CO_3])\\\Rightarrow 10^1=(7.5)/([H_2CO_3])\\\Rightarrow [H_2CO_3]=(7.5)/(10)\\\Rightarrow [H_2CO_3]=0.75\ \text{mM}`

`CO_2(g)+H_2O(l)\rightarrow H_2CO_3(aq)`

Concentration of
`H_2CO_3`,
`[H_2CO_3]=[CO_2]`

Concentration of
`CO_2`,
`[CO_2]=[H_2CO_3]=0.75\ \text{mM}`.