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EK Chem number 848.
There's a figure showing the titration curve of 0.1M carbonic acid with 0.1M NaOH. You don't really need the figure to answer my question, but if it helps you, this is page 91 of EK 1001 Gen Chem.
If the concentration of carbonic acid were greater, how would the titration curve change?
A. pH of the starting point would be lower and the pH of both equivalence points would be greater
B. pH of the starting point and both equivalence points would be lower
C. pH of both half equivalence points would be greater
D. pH of both half equivalence points would be lower
Answer is: A
I understand the first part of the answer (pH starting lower), but not the second part. Why wouldn't the equivalence points be at a lower pH too? EK's explanation is
I mean, I guess the explanation helps a little (I understand why more base = higher pH). Based on the explanation I understand how the second equivalence point (all CO32-) would be higher, but the conjugate of carbonic acid is still an acid (HCO3-), just not as strong of an acid as carbonic acid itself. So shouldn't its basic/acidic properties kind of cancel each other out and be at the same equivalence point as before?
There's a figure showing the titration curve of 0.1M carbonic acid with 0.1M NaOH. You don't really need the figure to answer my question, but if it helps you, this is page 91 of EK 1001 Gen Chem.
If the concentration of carbonic acid were greater, how would the titration curve change?
A. pH of the starting point would be lower and the pH of both equivalence points would be greater
B. pH of the starting point and both equivalence points would be lower
C. pH of both half equivalence points would be greater
D. pH of both half equivalence points would be lower
Answer is: A
I understand the first part of the answer (pH starting lower), but not the second part. Why wouldn't the equivalence points be at a lower pH too? EK's explanation is
The equivalence point is found from the concentration of conjugate base, so the conjugate base would be more concentrated at the equivalence point.
I mean, I guess the explanation helps a little (I understand why more base = higher pH). Based on the explanation I understand how the second equivalence point (all CO32-) would be higher, but the conjugate of carbonic acid is still an acid (HCO3-), just not as strong of an acid as carbonic acid itself. So shouldn't its basic/acidic properties kind of cancel each other out and be at the same equivalence point as before?