14.3 Acid-Base Reactions Acids and Bases

POINT > Define conjugate acid-base pairs POINT > Describe strength of acids and bases POINT > Identify amphoteric species POINT > Describe neutralization reactions

POINT > Define conjugate acid-base pairs Recall that Brønsted–Lowry reactions must have a proton donor (acid) and a proton acceptor (base) HCl + H2O  H3O+ + Cl-

POINT > Define conjugate acid-base pairs A Brønsted–Lowry acid must have a removable (acidic) proton: HCl, H2SO4, CH3COOH

POINT > Define conjugate acid-base pairs A Brønsted–Lowry base must have a pair of nonbonding electrons to accept the proton: NH3, OH-, H2O

POINT > Define conjugate acid-base pairs Reactions between acids and bases always yield their conjugate bases and acids HCl + NH3  NH4+ + Cl- When an acid donates a proton, its conjugate base is formed Cl- is the conjugate base of the acid HCl

POINT > Define conjugate acid-base pairs Reactions between acids and bases always yield their conjugate bases and acids. HCl + NH3  NH4+ + Cl- When an base accepts a proton, its conjugate acid is formed NH4+ is the conjugate acid of the base NH3

POINT > Define conjugate acid-base pairs Reactions between acids and bases always yield their conjugate bases and acids. HCl + NH3  NH4+ + Cl- The conjugate acid always has one more proton than its conjugate base

POINT > Define conjugate acid-base pairs Reactions between acids and bases always yield their conjugate bases and acids.

HF + H2O ↔ F- + H3O+ WB CHECK: What is the conjugate base of HF? What is the conjugate acid of H2O? What is the conjugate base of H3O+? What is the conjugate acid of F-?

POINT > Describe strength of acids and bases Strong acids completely dissociate in water: HCl + H2O  H3O+ + Cl- Their conjugate bases are therefore quite weak HCl HBr HI H2SO4 HNO3 HClO4 HClO3 These are the strong acids

POINT > Describe strength of acids and bases Weak acids dissociate only partially in water: CH3COOH + H2O ↔ H3O+ + CH3COO- Their conjugate bases are stronger bases

POINT > Describe strength of acids and bases The stronger an acid, the weaker its conjugate base The stronger a base, the weaker its conjugate acid The transfer of the proton in acid-base reactions favors the production of the weaker acid and base

POINT > Describe strength of acids and bases The transfer of the proton in acid-base reactions favors the production of the weaker acid and base HCl + H2O H3O+ + Cl- Compare the strengths of the acids (HCl and H3O+) and the bases (H2O and Cl-) using chart p. 459 The hydronium ion and chloride ion are weaker as acid and base respectively, so the arrow points…. 

POINT > Describe strength of acids and bases The transfer of the proton in acid-base reactions favors the production of the weaker acid and base CH3COOH + H2O H3O+ + CH3COO- Compare the strengths of the acids (acetic acid and H3O+) and the bases (H2O and acetate ion) using chart page 459 The acetic acid and water are weaker as acid and base respectively, so the arrow points…. 

HBr + H2O ? H3O+ + Br- WB CHECK: Predict the direction a reaction will take, based on acid and base strength: HBr + H2O ? H3O+ + Br-

HBr + H2O  H3O+ + Br- WB CHECK: Predict the direction a reaction will take, based on acid and base strength: HBr + H2O  H3O+ + Br- HNO3 + H2O ? H3O+ + NO3-

HBr + H2O  H3O+ + Br- WB CHECK: Predict the direction a reaction will take, based on acid and base strength: HBr + H2O  H3O+ + Br- HNO3 + H2O  H3O+ + NO3-

HCO3- HSO4- POINT > Identify amphoteric species As you may have noticed, water can act as an acid or a base. Such particles are called amphoteric: They tend to be weak as acids and weak as bases H2O HCO3- HSO4-

POINT > Describe neutralization reactions Strong acids and strong bases react with each other in neutralization reactions The protons released by strong acids combine with hydroxide ions released by strong bases to form water and a salt HCl + NaOH  H2O + Na+ + Cl-

WB CHECK: Predict the products of the strong acid-strong base reaction: HBr + Mg(OH)2  ? HNO3 + KOH  ?

Homework: Read Section 14.3 Pages 457-463 Section Assessment #1-3 Page 463