[fruity pebble]

Hi there! 
I am stumped on a problem asking me to identify whether HCO₃^- or CO₃^2- is a stronger conjugate base. I am not given any other information, and I was wondering how this would be possible. I know there is a rule that states the more oxygens are present, the stronger the acid/base, but I don't believe it applies here because there are not any hydrogens present in both of these conjugate bases. The question that comes after this asks whether NO₃^- or NO₂^- is stronger, and I also don't know how to approach this one either. Would the rule of more oxygens apply in this scenario? Any help would be greatly appreciated!
Thank you! 

[Borek]

Is there any relationship between strengths of the acid and its conjugate base?

You are given two bases - can you write their conjugate acids? What do you know about their strengths?

[fruity pebble]

Well I know that the conjugate acid of HCO₃^- is H₂CO₃, and I know that the conjugate acid of CO₃^2- is HCO₃^-, and I believe the Ka's decrease in value after successive losses of the H⁺ ion, meaning that HCO₃^- has to have a lower Ka than H₂CO₃ if I'm not mistaken. A lower Ka would mean a higher Kb, meaning a stronger base. So, the one with a lower Ka would be the stronger base, meaning the conjugate base of HCO₃^-, which was CO₃^2-. Hopefully my thought process is correct 

[Borek]

A bit convoluted what you wrote is But yes, looks like you got it right.

[fruity pebble]

Great, thank you for the guidance!