Need help with ambiguous wordings

[salemstein]

---

Members don't see this ad.

Asked which would lead to an increase in blood pH, consider these two scenarios:

1) conversion of CO2 into bicarb
2) excretion of H+ via kidney

How would I interpret what the question wants? For #1, though increasing bicarb would also lead to a simultaneous increase in H+, the equilibrium then would be driven back, reducing H+ and increasing pH. For #2, excretion has the immediate effect of raising pH, but then the system would be driven forward, lowering pH. Both may be correct, depending on the timing of the reaction. How would you go about interpreting the situation?

 

[theonlytycrane]

Just think about the immediate effect and not the countering response.

 

[aalamruad]

Asked which would lead to an increase in blood pH, consider these two scenarios:

1) conversion of CO2 into bicarb
2) excretion of H+ via kidney

How would I interpret what the question wants? For #1, though increasing bicarb would also lead to a simultaneous increase in H+, the equilibrium then would be driven back, reducing H+ and increasing pH. For #2, excretion has the immediate effect of raising pH, but then the system would be driven forward, lowering pH. Both may be correct, depending on the timing of the reaction. How would you go about interpreting the situation?

What do you mean "the equilibrium then would be driven back"?
You have CO2 which isn't acidic, you make it acidic by turning it into bicarb, so [H+] increases and pH decreases because you've essentially just added acid to the solution.

 

[salemstein]

What do you mean "the equilibrium then would be driven back"?
You have CO2 which isn't acidic, you make it acidic by turning it into bicarb, so [H+] increases and pH decreases because you've essentially just added acid to the solution.

I was saying because the [H+] increases, the reaction may be driven to decrease [H+]. Initially the pH decreases, then it increases again. I'm not sure which one to put for a question that asks what happens to pH: do I put the initial trend or the final trend?

 

[aalamruad]

I was saying because the [H+] increases, the reaction may be driven to decrease [H+]. Initially the pH decreases, then it increases again. I'm not sure which one to put for a question that asks what happens to pH: do I put the initial trend or the final trend?

Let's consider Le Chatlier's principle:

A + B --> C + D

If we add some A to an equilibrated solution (like increasing [H+] in your example), then we know that it will slightly decrease as it leads to increased production of C and D. However, it will NOT decrease to an amount that is less than when you initially added it. I think that's where you were getting confused.