Question

Which statement concerning the autoionization (self-ionization) of water is false?

2H₂O (l) --> H₃O+(aq) + OH-(aq)
O The reaction is an acid-base reaction according to Bronsted-Lowry theory
O Water is amphoteric (amphiprotic)
O A H₂O molecule can react as an acid by donating a proton.
O In this reaction H₃O+ and OH - are conjugate acid-base pair
O A H₂O molecule may react as a base by accepting a proton.

Answer 1

The false statement about the autoionization of water is that H₃O+ and OH⁻ are conjugate acid-base pair, which is incorrect; the correct pairs are H₂O/OH⁻ and H₃O+/H₂O.

Step-by-step explanation:

The statement concerning the autoionization of water that is false is 'In this reaction H₃O+ and OH⁻ are conjugate acid-base pair'. This statement is incorrect because H₃O+ (hydronium) and OH⁻ (hydroxide) are not a conjugate acid-base pair;

instead, H₂O (water) and OH⁻ (hydroxide) make up the conjugate pair where water acts as an acid, and H₃O+ (hydronium) and H₂O are the pair where water acts as a base. According to Brønsted-Lowry theory, an acid is a proton donor and a base is a proton acceptor.

Water is indeed amphoteric (or amphiprotic), meaning it can act as both an acid and a base. In its self-ionization, one water molecule donates a proton (acting as an acid), and another accepts a proton (acting as a base), thereby yielding hydronium and hydroxide ions in a state of equilibrium.

This equilibrium process occurs in all aqueous solutions, and the extent of the ionization is characterized by the ion-product constant for water (Kw).