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Level 126

Titration & pH


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pH scale
0 to 14, 7 is neutral
Acids
Compounds containing hydrogen that ionize to yield hydrogen ions in an aqueous solution
Bases
compounds that ionize to yield hydroxide ions in an aqueous solution
Arrhenius definition
acids add more H? to solution,
Bronsted-Lowry
acids donate H? (proton donor),
proton donor
BL acid
proton acceptor
BL base
conjugate acid
in reverse reaction can act as acid;
conjugate base
in reverse reaction can act as base;
Lewis acid
accepts lone electron pair
Lewis Base
A substance that can donate a pair of electrons to form a covalent bond.
Amphoteric
A substance that can act as both an acid and a base
pOH
= -log10 [OH?(aq)]
pH
= -log10 [H?(aq)]
pOH is 12
if pH is 2
pH + pOH = 14
formula pH when given pOH or formula for pOH when given pH
pH formulas
pH = -log[H?]
pOH formulas
pOH = -log[OH?]
[x]
M, concentration, or molarity, moles/liter
Strong Acids
Acids that completely ionize in aqueous solutions
Weak Acids
Acids that ionize only slightly in aqueous solutions
HCl (hydrochloric)
ex. strong acids
ex. strong bases
all hydroxides (OH?) of Group 1 or 2 (Alkali metals and Alkaline earth metals)
titration
A laboratory procedure in which a substance in a solution of known concentration is reacted with another substance in a solution of unknown concentration in order to determine the unknown concentration.
pH indicator
changes color when equivalence point is hit
equivalence point
equal number of moles of each substance (neutralized)
15x = .03x30
What is the concentration of 15 mL of HCl if it took 30.0 ml 30.0 M NaOH to reach equivalence point?
pH 7
a strong acid and a strong base have an equivalence point of
sour Taste (corrosive)
properties of acids (aq)
Why can acids conduct electric currents?
strong electrolytes, completely separated into ions in water
binary acid
contains only 2 different elements (H and an electronegative element), many common inorganic acids,
oxyacid
is a compound of H, O, and a nonmetal
ternary acids
contain 3 different elements
common industrial acids
sulfuric- most commonly produced industrial chemical, used in petrol refining, metallurgy, fertilizer manufacture, raw material production, car batteries, is an effect dehydrating agent
properties of bases
Taste bitter (caustic)
Arrhenius bases either
dissociate to release OH? in solution
electrolytes
all aqueous acids are
acid molecules are
polar, so water molecules attract H?, anions are left behind
strength of an acid
increases with increasing polarity (between H and anion) and decreasing bond energy (amount of energy needed to break bond)
aq solution of a weak acid
will have H?, anions, and dissolved acid molecules, reverse reactions occur simultaneously
organic acids
contain the acidic carboxyl group COOH, are weak acids generally
most aqueous bases
ionic compounds of metal cations and OH?,
strength of base
depends on extent of dissociation, also strong electrolytes,
Weak Bases
H2O, ROH, PR3, Halides, RS, N3, NC, RCOO
in NaOH
the BL base is OH? not NaOH, because OH? is what accepts the proton?
Bronsted-Lowry acid-base reaction
protons are transferred from one reactant (acid) to another (base)
monoprotic acid
can donate only one proton per molecule
polyprotic acid
can donate more than one proton per molecule
Diprotic Acid
Any acid that contains two ionizable protons
Triprotic Acid
Acids that contain three ionizable hydrogens.
both BL and Arrhenius
assume an acid contains/produces H?
Boron trifluoride
any compound with 3 valence electrons in the central atom that forms 3 covalent bonds can react as a Lewis acid
Lewis acid-base reaction
formation of a covalent bond between a Lewis acid and Lewis base
ammonia
Arrhenius, BL, and Lewish base
equilibrium systems
meaning that both forward and reverse reactions occur, involve conjugate pairs, Bronsted-Lowry
the stronger an acid is
the weaker its conjugate base so as not to compete with its acid
the stronger a base is
the weaker its conjugate acid so as not to compete with its base
proton transfer reactions favor
the production of the weaker acid and teh weaker base
for an acid base reaction to form products completely
the reactants must be much stronger as acids/bases than the products!!!
if water reacts with a stronger acid than water, then water acts as a base
if water reacts with a stronger base than water, then it will act as an acid
Hydroxyl group
A functional group consisting of a hydrogen atom joined to an oxygen atom by a polar covalent bond. Molecules possessing this group are soluble in water and are called alcohols.
neutralization example
antacid taken to soothe overly acidic stomach
strong acid-strong base neutralization
a salt and water are produced
spectator ions
appear on both sides of the overall ionic equation
a salt
ionic compound composed of a cation from a base and an anion from an acid
Acid Rain
Fossil Fuels contain the element sulphur or compounds of sulphur. This dissolves in rainwater; it thens reacts with water and oxygen to from a very dilute solution of sulphuric acid. This has some negative effects on the environment however:
self-ionization of water
two water molecules produce a H3O? and OH? by transfer of a proton
1.0 x 10?7
at 25°C concentrations of H3O? and OH?
ionization constant of water
Kw = [H+] [OH-] = 1.0 x 10^-14
ionization of water
increases as temperature increases
acid base indicators
obtain an approximate value for pH of a solution, compounds whose colors are sensitive to pH, indicators are either weak acids or weak bases
transition interval
pH range over which an indicator changes colo
pH meter
an electrode that is submerged in an aqueous solution; a voltage is measured that is pH dependent, so it can be determined directly
common indicators
methyl red, bromthymol blue, methyl orange, bromphenol blue, phenolpthalein, phenol red
end point
point in a titration at which an indicator changes color
Standard solution
a solution of known concentration that is used to combine with a sample of an unknown concentration
primary standard
highly purified solid compound used to check the concentration of the known solution in a titration
whether or not a substance will dissolve
what do the properties of a solvent and a solute determine?
agitation, temperature, particle size
stir only effects rate, can increase amount, crush
smaller particles have bigger volume
the bigger the surface area than
saturated solution
A mixture that contains as much dissolved solute as is possible at a given temperature.
solubility
A measure of how much solute can dissolve in a given solvent at a given temperature.
unsaturated solution
A mixture that contains less dissolved solute than is possible at a given temperature.
miscible
2 liquids that dissolve into one another
Immiscible
Conditions where two liquids will not dissolve in one another
supersaturated solution
A mixture that has more dissolved solute than is predicted by its solubility at a given temperature.
concentration
a mixture that has a large amount of solute in the solvent; a strong solution
dilute solution
A mixture that has only a little solute dissolved in it.
concentrated solution
A mixture that has a lot of solute dissolved in it.
molarity
# moles in solute / 1L of solution
diluting a solution reduces what?
the number of moles of solute per unit volume but the total number of moles of solute in solution does not change
percent by volume of solution is
volume of solute/the volume of solution
end in ide
hydro and ic
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end in ite
ic
end in ate
properties of acid
sour taste, active metals react with acids to produce hydrogen gas, release hydrogen ions in water, turns litmus and universal indicator red
Arrhenius Acid
Any substance that generates hydronium ions when added to water
Arrhenius base
A substance that produces hydroxide ions when added to water
ionizable
hydrogen atom that can form a hydrogen ion
hydronium ion
the ion that forms when a water molecule gains a hydrogen ion
bronsted-lowry acid
a hydrogen ion donor
bronsted-lowry base
a hydrogen ion acceptor
conjugate acid-base pair
2 ions or l\molecules relate by the loss or gain of one hydrogen ion
H3O+
Cis or Trans Addition, Markovnikov (OH, H) added
1.0 x10^-14
product of H+ and OH-
water molecules are highly
polar and in constant motion
acidic
a solution with a pH less than 7.0 is
Neutral
3rd degree substrate SN1 and E1
basic
a solution with a pH greater than 7.0 is
Self-Ionization
The reaction in which water molecules produce ions.
Neutral Solution
Any aqueous solution in which [H+] and [OH-] are equal.
Strong acid
An acid that donates its H+ ions to water in a reaction that goes completely to products
Weak Acid
_______ ionize only slightly in aqueous solutions.
small Ka
weak acids have
Ka is larger
if a degree of ionization of an acid is more complete
stronger the acid is the
larger the Ka value will be
Neutralization reaction
A chemical reaction between an acid and a base
titrations
experimental procedure in which a standard solution(solution of known concentration) is used to determine the concentration of an unknown solution
Acidic Solution
A solution in which [H+] is greater than [OH-]
Basic solution
A solution with a significant concentration of hydroxide ions
buffer
solution in which the pH remains fairly constant when small amounts of acid or base are added
limitless
buffers are not