Transcript 14 acid notes

ACIDS and BASES.
Not the stuff you already know!!!
Ways to define acids- Arrhenius
• Arrhenius is one way to characterize acids
and bases- it has to do with what they do
in water.
– Arrhenius Acid (AA)- is one that produces
H+ in water.
– Arrhenius Base (AB) is one that produces
OH- in water
– Limiting because only water solutions and
only one type of base, an OH
Some examples
• HCl + H2O H3O + + Cl • HNO3 + H2O  H3O + + NO3-
Bronsted Lowery acids
• A more general way to describe acids and bases
• An acid is anything that can donate a H+ ( a proton
donor)
• A base is anything that accepts a H+ ( a proton acceptor)
• That means acid and bases always occur in pairs, you
always have one acid and one base as reactants, and one
acid/one base on products
• A H+ is also called a hydronium ion. When added to
water write H3O+
Conjugate acids and bases
• A conjugate is anything on the product side that
remains after a proton has moved.
• HCl + H20  H3O + + ClAcid
base
conjugate acid
conjugate base
Keep in mind both bases can compete for the
proton, will need to determine which is stronger
to establish equilibrium
How to write them
• HCl + H2O
• HNO3 + H2O 
• H2SO 4
• Try pg 625
+ H2O
There is an equilibrium expression
for this!
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Ka = products over reactants,
Called an acid dissociation constant
Tells you how well the acid comes apart.
Ka< 1, mostly reactant ( doesn’t dissociate
well) WEAK ACID
• Ka >1 comes apart well, mostly product
STRONG ACID
• Ka = 1, even mix of the 2 in solution
Strong and weak, concentrated
and dilute
• Strong and weak have to
do with how reactive they
are
• Chart gives some idea
• Bases, OH is strong
• Nice to know (not have to
look up)
• HCl, NH3,H2SO4, H3PO4,
OH
• Concentrated and
dilute have to do with
how much substance
per how much water.
• This is molarity/
molality.
• High molarity is
concentrated
Other types of acids
• many acids are diprotic or triprotic- have 2 or 3
H. The first H to come off is usually strong, but
the rest are usually weak
• Oxyacids are H attached to a polyatomic ion
• Organic acids are carbon chains, usually weak
acids
• For very strong acids, Ka is not accurate because
the equilib. Is so far to right, and therefore not
very useful
How to get rid of more than one
Hydrogen
• If an acid has only one H+ to give away, it
is called monoprotic acid
– ( a Hydrogen without it’s electron is just a
proton)
• Examples include HCl, HF, HNO3
• If an acid has 2 Hydrogens to give away,
Diprotic, or 3, triprotic
– Examples include H2S, H2SO4 H3PO4
Base dissociation
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Ca(OH)2 becomes Ca + 2OHNa(OH) becomes Na + OHNH3 +H2O
NH4+ + OHCH3COO- + H2O becomes CH3COOH
+ OH-
• Strong bases have OH, weak have to
compete w/ water to get it, so weak
Ka and Kb
• Keeping in mind that Ka = products over reactants, and
large ka= strong acids,
• Kb is the strength of the base, is also products over the
reactants, and high Kb= strong bases.
• A strong acid will have a weak conj. Base, and
• a weak acid will have a strong conjugate base
• So the stronger the acid, the weaker its base, and if you
are a really strong acid ( HCl, H2SO4) don’t’ even have
Ka’s for it.
Water as acid and base
• Water is amphoteric, it can act as acid or base. It
also tends to come apart on it’s own.
• Autoionization is the term for water separating
into acid and base
• The Kw for water describes the number for this.
• H2O  H+ + OH• at 25 °
the [H+ ] = 1. x10 -7 and
•
[ OH-] = 1 x 10 -7,
• so the Kw= [H+ ][ OH-]
• So Kw = 1 x 10 -14
pH
• This auto ionization is the whole idea behind pH
• Kw is always 1 x 10-14 at 25°, but the ratio of H
and OH change with acids and base.
• Literally pH stands for the power of the
Hydrogen, and pOH stands for the power of the
OH.
• If H > OH, acid, if H<OH base, if H=OH
neutral.
pH continued
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Ok, so pH = -log [H+]
If [H+] = 1 x 10-3, pH =3 acid
If [H+] = 1 x 10-5, pH =5 acid
If [H+] = 1 x 10-9, pH =9 base
If [H+] = 1 x 10-14, pH =14 base
• See a pattern?
pH continued
• Ok, so pH = -log [H+]
• What if it isn’t quite that easy? Since pH is the power of
the H, even if it isn’t a “1” the pH will be close to the
exponant, but you will need to know how to use your
caluclator!!!
• If [H+] = 2 x 10-3, pH =2.66 acid
• If [H+] = 3.55 x 10-5, pH =4.45 acid
• If [H+] = 9.8 x 10-9, pH =8.009 base
• If [H+] = 6.99 x 10-14, pH =13.15 base
• You try them?
H and OH, pH and pOH
• H and OH are 2 parts of a whole, the whole being 1.0
x10-14,
• Remember that Kw = [H+ ] [OH-]
• and Kw = 1 x 10-14
• So…
• so if [H+ ]= 1 x 10-5, [OH-] = 1 x 10 -9
• so if [H+ ]= 1 x 10-3, [OH-] = 1 x 10 -11
• so if [H+ ]= 1 x 10-10, [OH-] = 1 x 10 -4
• so if [H+ ]= 1 x 10-2, [OH-] = 1 x 10 -12
• so if [H+ ]= 2.1 x 10-3, [OH-] = 4.76 x 10 -12
•
You try them too!
Neutralization
• Strong Acids and strong bases make water
and salt
• Not always NaCl salt. Just an ionic
compound.
• 2HF + Mg(OH)2
2H2O +MgF2
• 2H+ + 2F-
+ Mg+2 + 2OH-
2H2O +MgF2
Types of salts
• A strong acid and weak base = slightly
acidic salt
• Strong base and weak acid= basic salt
• Weak acid and base, varies
• When compounds have high oxidizing
metals, always slightly acidic ( Al+3,
Fe+3)
How concentration affects strength
• So far worked pH from {H3O}concent.
• What if given from chemical?
• .001 M HF?
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HF  H+ + F- , so HF & H+ are same, .001
But what if .001 H2SO4?
H2SO4  2H+ + SO4-2 ,
so H+ is double, .002
Oxides, some acids, some bases
• Metal oxides tend to make bases
• CaO, + H2O  Ca(OH)2,
K2O + H2O  KOH
• NONmetal oxides tend to make acids
• SO3 + H20  H2SO3 CO2 +H20  H2CO
Lewis acids/bases
• Even more broad in definition
• Electron pair donor, acceptor
• If has a unshared pair of electrons, is the Lewis
base
• Accepting the electrons, Lewis acid
• ( opposite of BL in theory)
• NH3, H2O, tend to have the e- pair, are bases
• H+, Ni+2, Al +3, acceptors, acid
Properties of acid and bases
• Acids
• Bases
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Taste sour
Turn pH paper red
pH of 0-6
Acids feel like water
Can be caustic
Foods like fruits, vinegar,
soda, yogurt
• Conduct electricity
• React with metals
Tastes bitter
Turn pH paper blue
pH of 8-14
Feel slippery
Can be caustic
Ammonia, soap, pickles
Conduct electricity
Do not react with metals
•Acids + bases = water +salt
Common names for acid and
base
• Acids
• Muratic acid- stomach
acids and cleaner
• Oranges, limes, lemon all
have citric acid
• Soda, sour candyphosphoric acid
• Walnuts- tannic acid
• Apples – malaic acids
• Vinegar- acetic acid
• Vitamin C- ascorbic acid
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Bases
Ca(OH)2 - tums
NH3 Ammonia
Lime CaCO3
Lye
NaOH
Industrial acids
• Muratic acid- HCl, cleaner of pools and
concrete, also of steel, food processing,
recovering Mg from sea water, and other food
creation processes. Stomach acid
• Sulfuric acid- most common industrial acid,
fertilizer production, car batteries, refining
process for many plastics, metals, paint, paper,
dyes etc. Great for dehydration process ( sugar
refining)
More industrial acids
• Nitric acid- Not stable, so less commonly used, used in
production of rubber and plasitcs, pharmacuitcals and
explosives.
• Phosphoric acid- beverages and candy, to clean food
equipment. also in fertilizers ( DNA is P based)
detergents and ceramics
• Acetic acid- glacial is very concentrated, vinegar.
Synthesizing chemicals used in plastic production, many
foods, production of essential amino acids. Also a
fungicide.
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12 M HCl is __________
(choose) strong/ weak and it is concentrated/dilute
.2 M H2SO4 is
(choose) strong/ weak and it is concentrated/dilute
1 M NaOH is ____________
(choose) strong/ weak and it is concentrated/dilute
12 M NH3 is _____________
(choose) strong/ weak and it is concentrated/dilute
.5 M H3PO4 is ___________________
(choose) strong/ weak and it is concentrated/dilute
15 M H3P is
(choose) strong/ weak and it is concentrated/dilute