Gen Chem Exam 3 Chapters 17-18

properties of acids

1. sour taste

2. can dissolve many metals

3. ability to neutralize bases

4. can turn blue litmus paper red

properties of bases

1. bitter taste

2. a soapy/slippery feel

3. ability to neutralize acids

4. can turn red litmus paper blue

what is the Arrhenius definition of an acid?

a substance that produces H⁺ in water

what is the Arrhenius definition of a base?

a substance that produces OH^- in water

what is the Bronstead-Lowry definition of an acid?

a substance that donates an H⁺

what is the Bronstead-Lowry definition of a base?

a substance that accepts an H⁺

in the Bronstead-Lowry definition, each base has a ____ ____ and each acid has a ____ ____

conjugate acid, conjugate base

what is a conjugate acid?

a substance that is created when a base accepts a proton

what is a conjugate base?

a substance that is created when an acid gives away a proton

strong acids

completely dissociate into its ions

HCl

strong acid

HBr

strong acid

HI

strong acid

HNO₃

strong acid

HClO₄

strong acid

H₂SO₄

strong acid

weak acids

only partially dissociate into its ions and form an equilibrium

HF

weak acid

HC₂H₃O₂

weak acid

HCHO₂

weak acid

H₂SO₃

weak acid

H₂CO₃

weak acid

H₃PO₄

weak acid

K_a

the equilibrium constant for a weak acid

the more H₃O⁺, the ____ the acid

stronger

the larger the K_a value, the ____ the weak acid

stronger

amphoteric

can act as an acid or base; water is an example

autoionization

H₂O_(l) + H₂O_(l) ⇌ H₃O⁺_(aq) + OH^-_(aq)

what is K_w?

the dissociation constant for water; 1.0 × 10^-14 at 25°C

if only water is present, then ____ = ____ = ____

[H⁺] = [OH^-] = 1.0 × 10^-7 M

what is present in all aqueous solutions?

OH^- and H⁺

acidic

[H⁺] > [OH^-]

basic

[H⁺] < [OH^-]

neutral

[H⁺] = [OH^-]

what is the pH scale?

a method of describing the acidity or basicity of a solution

equation for pH

pH = -log[H⁺]

equation relating pH and pOH

pH + pOH = 14

equation for pOH

pOH = -log[OH^-]

equation for [H⁺] or [OH^-]

[H⁺] = 10^-pH OR [OH^-] = 10^-pH

what do strong acids not have?

K_a values

strong base

completely dissociates in water; OH^- ion with a cation from column 1 and 2 on the periodic table

weak base

partially dissociates to form an equilibrium; steals an H⁺ from H₂O to form OH^-

K_b

the equilibrium constant for a weak base

salt

a compound formed by a neutralization reaction

anions

tend to form neutral or basic solutions

cations

tend to form neutral or acidic solutions

the conjugate base of an acid is _____

an anion

if the anion is the conjugate base of a strong acid, it will make the solution ____

neutral

if the anion is the conjugate base of a weak acid, it will make the solution ____

basic

the weaker the acid, the ____ its conjugate base

stronger

equation relating K_a and K_b

1.0 × 10^-14 = K_a x K_b

cations may act like ____ ____

weak acids

counterions of strong bases

pH neutral

conjugate acids of weak bases

acidic solutions

small, highly charged metals

weakly acidic solutions; transition metals 3⁺ or greater

neither the anion nor the cation act as an acid or base

neutral

the anion acts as a base but the cation doesn’t act like an acid

basic

the cation acts like an acid but the anion doesn’t act like a base

acidic

the cation acts like an acid and the anion acts like a base

depends on the relative strengths of each

buffer

a solution that resists change in pH when a strong acid or base is added

what does a buffer consist of?

a weak acid and its conjugate base or a weak base and its conjugate acid

conjugate base

the species remaining after an acid loses a proton

what does an added acid or base react with?

the acid or its conjugate base

common ion effect

the solubility of an ionic compound is lower in a solution containing a common ion than in pure water

Henderson-Hasselbalch equation

pH = pK_a + log([B]/[A])

equation for pK_a

pK_a = -log(K_a)

equation relating [H⁺] and [OH^-]

[H⁺] [OH^-] = 1.0 × 10^-14

equation relating pK_a and pK_b

pK_a + pK_b = 14

ideal buffer

occurs when the concentration of a weak acid or base equals the concentration of its conjugate base or acid

a buffer is more effective when the concentrations of the acid and base are ____

higher

buffer range

the effective range for any buffer is one pH unit above or below the pK_a value

buffer capacity

the amount of acid or base that can be added to a buffer without destroying its effectiveness

when does buffer capacity increase?

1. as the concentration of the weak acid gets closer in value to the concentration of the conjugate base

2. as the concentration of the weak acid and conjugate base increase

soluble

a compound is considered soluble is it dissolves in water

K_sp

the solubility product constant

molar solubility

(s), solubility expressed in molarity (mol/L)

can you use the K_sp values of different compounds to predict which compound is most soluble?

no: you cannot do this if they contain a different number of ions

yes: you can use K_sp to calculate s

what does a larger s value indicate?

the compound is more soluble

effect of pH on solubility

the solubility of an ionic compound with a strongly basic or weak basic anion increases with increasing acidity (decreasing pH)

precipitation

the formation of an insoluble precipitate