The number of conjugate acid base pairs present in aqueous solution of H3PO3

The number of conjugate acid-base pairs in an aqueous solution of H3PO3 can be determined by looking at the possible ionization steps of the acid.

1. The first ionization step: H3PO3 ⇌ H2PO3- + H+
2. The second ionization step: H2PO3- ⇌ HPO3^2- + H+
3. The third ionization step: HPO3^2- ⇌ PO3^3- + H+

From these steps, we can see that there are three conjugate acid-base pairs:

1. (H3PO3, H2PO3-)
2. (H2PO3-, HPO3^2-)
3. (HPO3^2-, PO3^3-)

So, there are 3 conjugate acid-base pairs present in an aqueous solution of H3PO3.