KA1 and KA2

[Do Yeun Park]

Could someone clarify why KA1 is greater than KA2 for the reaction H2CO3 + 2H2O --> CO3 2- +H3O +?

[805754009]

KA1 is greater than KA2 because after one proton has been removed, the molecule has a negative charge. This negative charge results in the molecule holding on to the remaining protons even tighter, as the the charges are attracted to each other. Therefore, in the second reaction, less of the reactants are going to be converted into the products due to the increased difficulty to remove a proton from the acid. Therefore the ratio of products to reactants in the second reaction (KA2) is going to be less than that of the first reaction (KA1).

[Daniel Tabibian 3K]

KA1 is greater than KA2 because after the acid loses one of its H+ ions, it has a negative charge. Due to this charge, it is less likely to give off another H+ than when it had a neutral charge, resulting in less H3O+ and a smaller KA2.

[Jenny Han 3F]

Agree with the other replies; also, this pattern is generally seen with every proton removal (KA1 -> KA2 -> KA3) since the more negative charge the molecule is, the greater attraction its protons have to it and the less likely deprotonation will occur.

[Nicole Ton 3C]

KA1 is greater than KA2 in this reaction because in the second reaction, we are removing the second proton from H2CO3. It is much harder to remove the second proton because after you remove the first proton, HCO3- has a negative charge which has electrostatic attraction to the positive charges. So, HCO3- doesn't dissociate as much as H2CO3, meaning the concentration of the products in KA2 is less than those in KA1. Since the concentration of the products are in the numerator in the KA equations, this makes it so KA2 is less than KA1.