Consider the reaction of nitrous acid in water where Ka = 4.0???10?4. HNO2(aq) +
ID: 493559 • Letter: C
Question
Consider the reaction of nitrous acid in water where Ka = 4.0???10?4. HNO2(aq) + H2O(l) NO2?(aq) + H3O+(aq) (a) Which two bases are competing for the proton? (Select all that apply.) HNO2 H2O NO2? H3O+ (b) Which is the stronger base? HNO2 H2O NO2? H3O+ (c) In light of your answer to (b), why do we classify the nitrite ion (NO2?) as a weak base? The nitrite ion is a base than water and produces solutions in water. When the nitrite ion is put into solution as the only major species, the competition is between the nitrite ion and the hydroxide ion for the proton. The resulting equilibrium lies far to the left producing a Kb value of one. is the strongest base possible in water. Species that are classified as weak bases are stronger bases than water but are weaker bases than . Use an appropriate reaction to justify your answer. (Include states-of-matter at 25°C and 1 atm in your answer.)
Explanation / Answer
Weak acid HNO2
HNO2 + H2O <==> NO2- + H3O+ Ka
Conjugate base NO2- of a weak acid HNO2 is also a weak base
(a) NO2- and H2O compete for the proton
(b) H2O is a stronger base
(c) Conjugate base NO2- of a weak acid HNO2 is also a weak base
(d) NO2- hydrolze in water to produce OH- ion
NO2- + H2O <==> HNO2 + OH-
so OH- a stronger base than NO2- now competes with NO2- for the proton.