Consider the reaction CO3^-2+H2O<==>HCO3^+OH^-. Kb for CO3^-2 is 2.1x10^-4 at 25 Celsius . What is Ka for the HCO3^- ion at 25 Celsius?

wouldn't that be 1/2.1E-4? That's the reverse of the equation.

To find the Ka value for the HCO3- ion, we can use the relationship between Ka and Kb for a conjugate acid-base pair. The equation is as follows:

Ka × Kb = Kw

where Kw is the ion product of water, which is equal to 1.0 × 10^-14.

In this case, we are given the Kb value for the CO3-2 ion, which is 2.1 × 10^-4. To find the Ka value for the HCO3- ion, we need to rearrange the equation:

Ka = Kw / Kb

Plugging in the known values, we have:

Ka = (1.0 × 10^-14) / (2.1 × 10^-4)

Calculating this expression will give you the value for Ka.