CH110

Chapter 15 Notes

Acids and bases expanded; definitions were in Chapter 2; strength in Chapter 4

Using your knowledge of acid-base reactions and reaction equilibria, mathematical expressions of acid-base equilibria can be given

Remember, Arrhenius said acids donated protons and bases donated hydroxide ions

Bronsted said that acids are proton donors and bases are proton acceptors

(Lewis definitions involve electron pairs)

Bronsted theory required no water

Conjugate acid-base pairs are apparent in an acid-base reaction at equilibrium

Ex. NH₃ + H₂O in eq. with NH₄⁺ + OH^-

NH₄⁺ is the conjugate acid of the base NH₃

OH^- is the conjugate base of the acid H₂O

So a conjugate base is an acid minus a proton

And a conjugate acid is a base plus a proton

A substance that can act as both an acid and a base is called amphoteric, or (as your book more precisely calls it here) amphiprotic

The K for an acid-base equilibrium is called either the acid or base ionization constant (depending on the molecules involved)

Strong acids have a large K_a and strong bases have a large K_b (why???)

A strong acid has a weak conjugate base (why???)

A strong base has a weak conjugate acid

Factors affecting acid strength for binary acids

Bond strength

Atomic radius

Ionic or covalent character- electronegativity differences

Factors affecting acid strength for other acids and bases

Electron Withdrawing Groups (EWG's) attached to carboxylic acids

EWG's on amines

The pH scale

lowercase "p" and uppercase "H"

-log[H⁺]

Calculations

Polyprotic acids (15.5)

Ions as acids and bases (15.6)

Common ion effect (LeChatelier revisited)

Buffers (prepare for lab next semester) (Fig. 15.8)

Indicators (prepare for lab next semester) (Fig. 15.15)

Neutralization reactions and titration curves (prepare for lab next semester)