1.4. Properties of Acids and Bases

Recall definition of acid and bases based on Arrhenius model.

Acid:

• substance that contains hydrogen and dissociates (ionises) in water to give H+ ions.More H+ = More acidic

Base:

• substance that contains hydroxyl grojps and dissociates (ionises) in water to give OH- ions (hydroxide)

Why is Arrhenius model not completely realistic?

• did not account for ammonia (NH3) as it is a base without OH- and some other substances as well.

• only works in water and not gases or non-water solvents

What is the Bronsted-Lowry Model?

Acids:

• donates protons when reacting with water

Bases:

• accepts protons when reacting with water

BAADies

What is H3O+?

H+ and hydronium ions (H3O+) are used interchangeably when talking about acids donating protons.

Distinguish between Monoprotic, Polyprotic (Diprotic and Triprotic) acids and Amphiprotic.

Monoprotic:

• can only donate one proton

Polyprotic:

• donate multiple protons but not all at once, in steps

• Di = 2, Tri = 3

Amphiprotic:

• can both donate OR receive a proton.

• E.g.water can be both acid and base

What are conjugate bases and acid?

in reversible reaction, after the forward reaction:

Acid → conjugate Base

Base → conjugate Acid

Distinguish between strength and concentration/dilution of the Acid and Base?

Strength:

• How much it dissociates.

Concentrated/Dilute:

• amount of solute in solvent.

Distinguish between Strong acid and Weak acid? (4 points each)

Strong Acid:

• 100% dissociates

• Fast ROR

• pH low (~0)

• High conductivity

Weak Acid:

• Partially dissociates (reversible)

• Slow ROR

• pH high but lower than 7

• Low conductivity

Distinguish between Strong and Weak bases. (4 points each)

Strong Base:

• 100% dissociates

• Fast ROR

• pH very high (~14)

• High conductivity

Weak Base:

• Partially dissociates (reversible)

• Slow ROR

• pH lower but higher than 7

• Low conductivity

Recall the table of Strong and Weak acids and bases (Hint: HNS, CCP, G1BC, AA)