Chapter 12: Introduction to Acids and Bases Flashcards
acids tend to
taste sour, react with active metals to produce H2 (g), and turn litmus red
bases tend to
taste bitter, produce solutions that feel slippery, and turn litmus blue
acid/base indicators
chemical compounds that change color in acidic, basic, or neutral environments
both acids and bases dissociate to form ions in aqueous solution, therefore they are
electrolytes
acids and bases that completely ionize/dissociate (100%) are
strong
acids and bases that do not completely ionize in aqueous solution are
weak
Arrhenius definition (acid)
an acid is a hydrogen-containing substance that dissociates to produce hydrogen ions (H+), which are typically present as H3O+ in water
acidic solutions have a higher [H3O+]
Arrhenius definition (base)
a base is a substance that dissociates to produce hydroxide ions (OH-) in aqueous solution
basic solutions have a higher [OH-]
neutral solutions have
[H3O+] = [OH-]
H2O can function as
both an acid and a base; water is essentially a non-electrolyte, but there is a small amount of dissociation
allows for the autoionization of water
polyprotic acids
can release more than one H+ into aqueous solution
acids that can only release one proton into solution are
monoprotic acids (e.g., hydrochloric acid, hydrobromic acid, and nitric acid)
diprotic acids such as sulfuric acid and carbonic acid can release
two protons
triprotic acids such as phosphoric acid can release
three protons
Bronsted-Lowry definition (acid)
an acid is a proton donor
Bronsted-Lowry definition (base)
a base is a proton acceptor
the ionization of weak acids is an example of an
equilibrium reaction
when describing an acid-base equilibrium, we refer to the acid and base on the right-hand side of the chemical equation as the
conjugate acid and conjugate base
the conjugate acid is formed when
a base gains a proton (H+); it’s what forms when a base accepts a proton
the conjugate base is formed when
an acid loses a proton; it is what remains of the acid after it has donated a proton
the conjugates of weak acids are
basic; they can act as a weak base and accept protons from water and increase the OH- concentration
in acid-base neutralization reactions, an acid and a base combine to produce
water and an ionic compound (salt); the formation of water is the driving force for the neutralization reaction
double-displacement reaction
acids react with pure metals to produce
hydrogen gas (single-displacement reaction)
precious metals (silver, gold, and platinum) do not react with acid
nonmetal oxides
compounds that contain a nonmetal covalently bonded to one or more oxygen atoms; typically react with water to form acidic solutions
metal oxides
compounds that consist of a metal element chemically bonded to oxygen; reacts with water to form basic solutions
acids react with carbonates to produce
water, carbon dioxide, and a salt
autoionization of water
the process in which water molecules spontaneously dissociate into hydronium ions and hydroxide ions
a water molecule donates a proton to another water molecule to form ions
the autoionization of water yields
the same number of hydronium and hydroxide ions; [H3O+] and [OH-] = 1.0 x 10^-7 M
the equilibrium constant expression for the autoionization of water is
Kw; Kw = [H3O+][OH-] = 1 x 10^-14 M at 25 C
a common way to express acidity and basicity is
pH
pH is a measure of
[H3O+] aka [H+]; pH = -log[H3O+]
-log[1.00 x 10^-7] = 7 (neutral)
pOH =
-log[OH-]; since [OH-] = 1.0 x 10^-7 M, pOH = 7 (neutral)
pH + pOH =
14
if the pH decreases, the [H3O+]
increases; the solution is more acidic than neutral water
remember: pH is the negative logarithm of the [H3O+]
pH < 7.00
the solution is acidic
pH = 7.00
the solution is neutral
pH > 7.00
the solution is basic
a change of 1 pH represents
a tenfold change in [H3O+]; a decrease in pH by 1 unit increases [H3O+] by a factor of 10 & an increase in pH by 1 unit decreases [H3O+] by a factor of 10
because strong acids dissociate completely, the acid molecules break apart to form
hydronium ions and anions (conjugate base); thus, [strong acid] is the same as [H3O+]
titration
an analytical technique used to precisely determine the concentration of an acid or base by measuring the volume required for a neutralization to occur
used to determine the molarity of an unknown acid or base
buffer
a solution containing a mixture of acidic and basic components that resists changes in pH; adding acid or base in a buffered solution causes a smaller pH change
two common combinations of buffers are
a mixture of a weak acid and its conjugate base & a weak base and its conjugate acid
the pH of a buffer solution depends on
the relative amounts of the acid and base components
the weaker the acid,
the stronger the conjugate base
weak acids leave a conjugate base w/ a greater ability to accept protons
the stronger the acid,
the weaker the conjugate base
there is no reverse reaction with a strong acid because
the strong acid completely dissociates, going all the way to the right side of the reaction; dissociation is essentially irreversible because of the strong tendency to donate a proton
the salt of a strong acid forms a
neutral solution because the conjugate base is very weak and does not interact with water in a way that would alter the pH
the salt of a weak acid forms a
basic solution because the conjugate base is strong enough to react with water and increase the [OH-], thus increasing the pH
since the salt of a weak acid is basic, a neutralization reaction can take place with
an acid; the conjugate base of the weak acid (present in the salt) can neutralize the H⁺ ions from the acid, reforming the weak acid in hydrolysis
hydrolysis
a chemical reaction in which a substance reacts with water to produce either H+ or OH- ions, affecting the pH (acidic, basic, or neutral hydrolysis)
