This question is under a chemistry unit of Acid-Base Theories.Write equations to show how the hydrogen sulfide ion,HS−,can react with water.First show the ion acting as an acid.Then show the ion...

This question is under a chemistry unit of Acid-Base Theories.

Write equations to show how the hydrogen sulfide ion,HS−,can react with water.First show the ion acting as an acid.Then show the ion acting as a base.

Expert Answers
hnystrom eNotes educator| Certified Educator

When a substance acts as an acid it is donating a proton or H+ to another molecule.  Stong acids are those that readily give up protons and weak acids are those that tends to hold on to them.  HCl is a stong acid because most of the molecules give up H+ to the water creating a solution of H3O+ and Cl-.  Acetic acid Ch3COOH is a weak acid because by percent fewer molecules give up the final H+ to form H3O+.

When a substance acts as a base it accepts a proton.  Hydroxides are bases because they tend to ionize in water releasing OH-.  These readily accept protons to form H2O.  NaOH is a strong base because most of the molecules dissociate into Na+ and OH-.  All alcohols, methyl alcohol is CH3OH, are hydroxides but we don't think of them as bases because they tend to hang on to the OH- and not dissociate.

A reaction in water where HS- acts as an acid is when it gives up the H+.  So HS- + H2O > S-- + H3O+ .

A reaction in water where HS- acts as a base when it accepts another proton.  So HS- + H2O > H2S + OH-.