The fully hydrated form of sodium sulfate is the decahydrate Na2SO4 • 10 H2O. This compound dehydrates (loses some water of hydration) when heated. A partially dehydrated sodium sulfate sample was found to have a molar mass of 323.1 g/mol. How many water molecules are found per formula unit in this sample? (Hint: determine n in Na2SO4 • n H2O)

There are a couple of ways to define acids

and bases

ν Brønsted-Lowry acids and bases

ν Acid: H+ ion donor

ν Base: H+ ion acceptor

ν Lewis acids and bases

ν Acid: electron pair acceptor

ν Base: electron pair donor

ν In most acid-base systems, water may play a

role as either an acid (H+ donor) or a base (H+

acceptor)

Water as an acid

H2O(l) + B(aq) ↔ OH-

(aq) + HB+(aq)

Water as a base

H2O(l) + HA(aq) ↔ H3O+(aq) + A-

(aq)

Explanation:

Acids react with bases and vice versa

ν All acids and bases come with a conjugate

pair—a base or acid, respectively, that is

formed in conjunction with the original

species

Examples

HCl(aq) + H2O(l) ↔ H3O+(aq) + Cl-

(aq)