Chapter 14 Acids and Bases 14.2 Brønsted−Lowry Acids and Bases Learning Goal Identify conjugate acid−base pairs for Brønsted−Lowry acids and bases. © 2014 Pearson Education, Inc.

Brønsted−Lowry Acids and Bases According to the Brønsted–Lowry theory, an acid donates a proton (H+) a base accepts a proton (H+) Free H+ ions do not exist in water. The H+ ion is so strong that it bonds to a water molecule and forms a hydronium ion, H3O+ © 2014 Pearson Education, Inc.

Brønsted−Lowry Acids A solution of hydrochloric acid forms when H+ transfers from hydrogen chloride to water. Water is acting as a base in this reaction. © 2014 Pearson Education, Inc.

Ammonia (NH3) reacts with water in which Brønsted−Lowry Bases Ammonia (NH3) reacts with water in which NH3 acts as the base, accepting H+ from water H2O acts as an acid in this reaction, donating H+ to NH3 © 2014 Pearson Education, Inc.

Conjugate Acid−Base Pairs In an acid–base reaction, there are two conjugate acid–base pairs: an acid that donates H+ to form its conjugate base conjugate acid–base pair 1 HA + B A− + BH+ conjugate acid–base pair 2 a base that accepts H+ to form its conjugate acid © 2014 Pearson Education, Inc.

Conjugate Acid−Base Pairs In the reaction of HF and H2O, we can identify the conjugate acid–base pairs as HF/F− along with H3O+/H2O. © 2014 Pearson Education, Inc.

Conjugate Acid−Base Pairs In the reaction of NH3 and H2O, we can identify the conjugate acid–base pairs as NH3/NH4+ along with H2O/OH−. © 2014 Pearson Education, Inc.

A. Write the conjugate base of the following: 1. HBr 2. H2S 3. H2CO3 Learning Check A. Write the conjugate base of the following: 1. HBr 2. H2S 3. H2CO3 B. Write the conjugate acid of the following: 1. NO2− 2. NH3 3. OH− © 2014 Pearson Education, Inc.

A. Write the conjugate base of the following: 1. HBr Br− 2. H2S HS− Solution A. Write the conjugate base of the following: 1. HBr Br− 2. H2S HS− 3. H2CO3 HCO3− B. Write the conjugate acid of the following: 1. NO2− HNO2 2. NH3 NH4+ 3. OH− H2O © 2014 Pearson Education, Inc.

Guide to Writing Conjugate Acid−Base Pairs © 2014 Pearson Education, Inc.

Identify the conjugate acid−base pairs in the following reaction: Learning Check Identify the conjugate acid−base pairs in the following reaction: HI(aq) + NH3(aq) I−(aq) + NH4+(aq) © 2014 Pearson Education, Inc.

Solution Identify the conjugate acid−base pairs in the following reaction: HI(aq) + NH3(aq) I−(aq) + NH4+(aq) Step 1 Identify the reactant that loses H+ as the acid. In the reaction, HI loses H+ to form the product I−. Thus HI is the conjugate acid, and I− is its base. © 2014 Pearson Education, Inc.

Identify the conjugate acid−base pairs in the following reaction: Solution Identify the conjugate acid−base pairs in the following reaction: HI(aq) + NH3(aq) I−(aq) + NH4+(aq) Step 2 Identify the reactant that gains H+ as the base. In the reaction, NH3 gains H+ to form the product NH4+. Thus NH3 is the conjugate base, and NH4+ is its acid. © 2014 Pearson Education, Inc.

Identify the conjugate acid−base pairs in the following reaction: Solution Identify the conjugate acid−base pairs in the following reaction: HI(aq) + NH3(aq) I−(aq) + NH4+(aq) Step 3 Write the conjugate acid−base pairs for each. HI/I−, NH3/NH4+ © 2014 Pearson Education, Inc.