Write an equation to show how hco3 - can act as a base with hs - acting as an acid.

The equation for the reaction;

HCO3 - + HS - = CO2 + H2O + S^2-

A bicarbonate ion is amphoteric; it can act as either an acid or base in water.

HCO3 - is the conjugate base of H2CO3, a weak acid, and the conjugate acid of the carbonate. HCO3 - acts as a base when mixed with a compound that is more acidic than itself and as an acid when mixed with a compound that is more basic than itself.