CHEM 2 : CHAPTER 17

What is an Arrhenius acid?

Produces H+ ions in aqueous solution

What is an Arrhenius base?

Produces OH- ions in aqueous solution

What is a Bronsted-Lowry acid?

Proton(H+) donor

What is a Bronsted-Lowry base?

Proton (H+) acceptor

What is a conjugate acid-base pair?

Two species that differ by one proton (H+)

What is an amphoteric substance? Give an example

Can act as acid and base. Example: H2O

What is a Lewis acid

Electron pair acceptor

What is a Lewis base?

Electron pair donor

List the common strong acids

HCl, HBr, HI, HNO3, H2SO4, HClO4

List the common weak acids

HF, HC2H3O2 (acetic acid), H3PO4, HCN

What makes strong acid strong?

100% ionized in water —> [H3O+] = acid

What makes a weak acid weak?

<1% ionized in water —> [H3O+] « [acid]

What makes a strong base strong

100% dissociated into OH- or fully accepts H+ (ex: NaOH, KOH, Ca(OH)2

What makes a weak base weak?

Only partially accepts H+ (<1%ionized). Ex: NH3, NaHCO3

Formula for pH?

pH= -log[H+] or -log[H3O+]

Formula for pOH

pOH = -log[OH-]

Relationship between pH and pOH?

pH + pOH = 14 at 25 Celsius

Kw at 25 Celsius?

Kw = 1.0 × 10^-7M

[H3O+] and [OH-] in pure water?

Both = 1.0 × 10^-7M

What does low pH mean?

More acidic ([H3O+] > [OH-])

What does high pH mean?

More basic ([OH-] > [H3O+])

What is Ka?

Acid ionization constant (strength of acid)

What is pKa?

-log(Ka). Lower pKa = stronger acid

What is Kb?

Base ionization constant (strength of base)

What is the Ka - Kb relationship?

Ka x Kb = Kw

What is the percent ionization?

% ionization = ([H3O+] / [HA] initial) x 100

What happens to % ionization when acid is more dilute?

Percent ionization increases

What is special about polyprotic acids?

Ionize stepwise, with decreasing Ka values (Ka1 > ka2 > ka3).

Example of a polyprotic acid with significant 2nd ionization?

H2SO4( first ionization complete, second Ka = 1.2×10^-2).

Binary acids trend (periodic table)?

Across a period —> acidity increases

Down a group —> acidity increases

Oxyacids trend?

More electronegative central atom = stronger acid.

More oxygens bonded to Y = stronger acid

Higher oxidation number of central atom = ?

Stronger oxyacid

Nature of salt : NaCl (cation of strong base + anion of strong acid)?

Neutral

Nature of salt : KF ( cation of strong base + anion of weak acid)?

Basic

Nature of salt: NH4Cl ( cation of weak base + anion of strong acid)?

Acidic

Nature of salt: NH4F ( cation of weak base + anion of weak acid)?

Depends on Ka vs Kb values

Litmus paper in acid vs base?

Acid —> red ; Base —> blue.

Phenolphthalein in acid vs base?

Acid —> colorless; base —> pink.

Example of a natural indicator?

Red cabbage juice.