'Is the amphoteric substance C2O4H- more likely to act as an acid or a base, and why?'
I was given the Ka of C2O4H- as 6.4 x 10^-5, so I calculated its pKa as about 4.19. Then I found its pKb as about 9.80, which makes its Kb about 1.56 x 10^-10. Thus, I concluded that it is more likely to act as an acid because its Ka is higher than its Kb. Am I on the right track here, or am I missing something?
Thanks!
I believe you are on the right track. Here is an excellent example using HCO3^- plus practice problems on the two hydrogen phosphate ions from H3PO4.
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch17/either.php
Well, it seems like you've done your calculations correctly, but let me put it in a more "colorful" way for you. Picture the amphoteric substance C2O4H- as a confused circus performer standing on a seesaw. On one end, you have acids, and on the other end, you have bases. Now, if this confused circus performer is more likely to lean towards the acid end, it means it is more likely to act as an acid. And based on your calculations, it seems like this performer has a strong preference for acid acts because its Ka is indeed higher than its Kb. So, you're definitely on the right track! Hope this helps, and enjoy your circus chemistry journey!
You are on the right track. Based on the information you provided, the amphoteric substance C2O4H- is more likely to act as an acid because its Ka (acid dissociation constant) is higher than its Kb (base dissociation constant).
An amphoteric substance is capable of acting as both an acid and a base, depending on the circumstances. When determining whether an amphoteric substance acts as an acid or a base, you can compare the relative values of its Ka and Kb.
In this case, since the pKa is roughly 4.19 and the pKb is approximately 9.80, it confirms that the substance is more likely to act as an acid. A higher value of Ka indicates a stronger acid, while a higher value of Kb indicates a stronger base.
Therefore, since the Ka of C2O4H- is higher than its Kb, it is likely to act as an acid.
Yes, you are on the right track! Based on the information you provided, you correctly calculated the pKa and pKb values for the amphoteric substance C2O4H-. To determine whether it is more likely to act as an acid or a base, you compared the magnitude of its Ka and Kb values.
In general, when an amphoteric substance has a higher Ka value (acid dissociation constant) compared to its Kb value (base dissociation constant), it is more likely to act as an acid. This is because the equilibrium between the conjugate acid and base forms of the substance favors the acid form.
In your case, you found that the pKa of C2O4H- is approximately 4.19, which corresponds to a Ka value of 6.4 x 10^-5, and the pKb is approximately 9.80, which corresponds to a Kb value of 1.56 x 10^-10. Since the Ka value is higher than the Kb value, C2O4H- is indeed more likely to act as an acid rather than a base.
Remember that pKa and pKb values are indicators of the strength of acid and base dissociation, respectively. The higher the Ka or pKa value, the stronger the acid, and the lower the Kb or pKb value, the stronger the base.
Overall, your analysis is correct, and you correctly determined that C2O4H- is more likely to act as an acid. Keep in mind that this conclusion was based on the comparison between the Ka and Kb values, and further experiments or analysis may be required for a more comprehensive understanding of its acidic or basic behavior.