Bicarbonate can also absorb hydrogen ions: HCO3-+H+=H2CO3.

Therefore, in the solution, C(H+)+C(H2CO3)=C(CO32-) is brought into the equilibrium constant.

C(H+)+C(H+)(HCO 3-)/k 1 = K2C(HCO 3-)/C(H+)

After removing the denominator: k1c 2 (h+)+c (HCO 3-) C2 (h+) = k12c (HCO 3-)

Let the concentration of sodium bicarbonate =x, and solve the equation: C 2 (h+) = k1K2x/(k1+x).

k 1 & lt； & ltx can be ignored, so C2 (h+) = k1k2x/x = k1k2.

That is, under C(H+)= radical sign, K 1K2.