Exception for the use of Ka1 for polyprotic acids?
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Exception for the use of Ka1 for polyprotic acids?
Hello! In lecture I remember Dr. Lavelle stating that for polyprotic acids, calculations should use the Ka value of the first deprotonation because the following deprotonations don't have a significant Ka value in comparison. However, I remember there being some discussion around the Ka values of sulfuric acid (H2SO4), since it has larger following Ka values for subsequent deprotonations. Is H2SO4 an exception to the rule of using only the first Ka in calculations? If so, what would that look like in a calculation (i.e. multiple ice tables to find equilibrium concentration, one for each deprotonation?). Or, do we still just use the first Ka value?
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Re: Exception for the use of Ka1 for polyprotic acids?
In the case of sulfuric acid (H2SO4), it's an exception to the general rule for polyprotic acids. You consider both ionization steps in calculations because the second ionization has a significant Ka value. Also, you should use multiple ICE tables, starting with the initial concentration of H2SO4 for each ionization step.
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