Let's analyze the given equation to understand the changes in pH, bicarbonate ions ([tex]$HCO_3^-$[/tex]), and [tex]$PCO_2$[/tex] levels:
[tex]\[CO_2 + H_2O \leftrightarrow H_2CO_3 \leftrightarrow H^+ + HCO_3^-\][/tex]
Here's the breakdown step-by-step:
1. Understanding the Chemical Equation:
- When [tex]$CO_2$[/tex] (carbon dioxide) dissolves in water ([tex]$H_2O$[/tex]), it forms carbonic acid ([tex]$H_2CO_3$[/tex]).
- Carbonic acid can dissociate into hydrogen ions ([tex]$H^+$[/tex]) and bicarbonate ions ([tex]$HCO_3^-$[/tex]).
2. Impact on pH:
- pH is a measure of the hydrogen ion concentration: [tex]\( \text{pH} = -\log[H^+] \)[/tex].
- An increase in [tex]$H^+$[/tex] ions will lower the pH (making it more acidic).
3. Impact on Bicarbonate Ions:
- The dissociation of carbonic acid results in more bicarbonate ions.
4. Impact on [tex]$PCO_2$[/tex] Levels:
- [tex]$PCO_2$[/tex] represents the partial pressure of carbon dioxide. An increase in [tex]$CO_2$[/tex] will drive the reaction to produce more carbonic acid and subsequently more hydrogen and bicarbonate ions.
From the given information, if [tex]$PCO_2$[/tex] levels increase:
- This will shift the equilibrium towards the production of more [tex]$H_2CO_3$[/tex], and subsequently more [tex]$H^+$[/tex] and [tex]$HCO_3^-$[/tex].
As a consequence:
- pH will decrease (due to the increase in [tex]$H^+$[/tex] ions),
- Bicarbonate ions ([tex]$HCO_3^-$[/tex]) will increase,
- [tex]$PCO_2$[/tex] levels will increase.
Therefore, the correct choice is:
c. pH will decrease, bicarbonate ions will increase, and [tex]$PCO_2$[/tex] levels will increase.
