Foods with a sour taste - may be due to the presence of acids
lactic acid
acetic acid
phosphoric acid
citric acid
malic acid
tartaric acid
bitter tasting -- be careful about tasting any unknown substance
household ammonia
sodium hydroxide - lye
milk of magnesia - magnesium hydroxide
- Acids
common properties based on their aqueous solutions
a) aqueous solution of acids have a sour taste -
be careful about tasting any unknown substance
b) acids change the color of acid-base indicators
pH paper, blue litmus to red
c) some acids react with active metals to release hydrogen gas
e.g. Ba (s) + H 2 SO 4 ---> BaSO 4 + H 2
d) acids react with bases to produce salts and water
e) some acids conduct electric current
- Acid
Nomenclature
binary acid - definition
hydrogen halides in water
table 15-1 page 454
hydro + root of halogen + ic + word acid
oxyacid - definition
Table 15-2 page 455
know formulae of all of the -ic acids in table 15-2
one more oxygen, add prefix per to name of ic acid
one less oxygen, change suffix ic to ous
two less oxygen, change suffix ic to ous and add prefix hypo
- Acid
Nomenclature
- Some Common
Industrial Acids
- Sulfuric
Acid
Most commonly produced industrial chemical in the world
Used in petroleum refinery and metallurgy and the manufacture of fertilizers
The acid used in auto batteries
Attracts water and used as a dehydration agent
- Nitric
Acid
Volatile, unstable liquid
Stains proteins yellow
Used in making explosives, many of which are nitrogen containing compounds
Also used in making rubber, plastics, dyes and pharmaceuticals.
Solution turns from colorless to yellow when left standing for long periods -- due to the decomposition to brown nitrogen dioxide gas.
- Phosphoric
Acid
phosphorus + nitrogen + potassium found in fertilizers
most of this acid that is produced is used in fertilizers and animal feed
has a pleasant but sour taste and is not toxic
used as a flavoring agent in beverages and as a cleaning agent for dairy equipment
also used in the manufacture of detergents and ceramics
- Hydrochloric
Acid
produced in the stomach as a digestive juice
used to pickle iron and steel
general cleaning agent in industry
also used as muriatic acid
- Acetic
Acid
clear, colorless, pungent smelling liquid - glacial acetic acid
pure acetic acid freezes at 17 o C
forms crystals in a cold room
white vinegar - 4 to 8% acetic acid
used in synthesizing chemicals used in the manufacture of plastics
also used as a fungicide
- Sulfuric
Acid
- Bases
Properties
a) bitter taste
b) change the color of acid base indicators e.g. pH paper, red litmus to blue
c) slippery feeling
d) react with acids to produce salt + water (neutralization rxn)
e) conduct electric current - ions in solution
- Arrhenius Acids
and Bases
Arrhenius acid - definition
Arrhenius base - definition
acids due to ionization
bases usually due to dissociation, exception is ammonia
- Aqueous
Solutions of Acids
Arrhenius acids are molecular compounds with one or more ionizable hydrogens
Water solutions are called aqueous acids
Pure aqueous acids are electrolytes.
HNO 3 + H 2 O ---> H 3 O 1+ + NO 3 1-
HCl + H 2 O ---> H 3 O 1+ + Cl 1-
Figure 15-6 page 459
- Strength
of Acids
strong acid - definition
examples: perchloric acid, nitric acid
depends on polarity of bond between hydrogen and the anion to which is is bonded
more polar and less bond energy means greater acid strength
weak acid - definition
examples: hydrocyanic acid
HCN + H 2 O = H 3 O 1+ + CN 1-
where the equilibrium is far to the left i.e. many molecules, few ions
table 15-3 page 460
strong acids are assumed to ionize completely to produce at least one hydrogen (hydronium) ion
in table 15-3 note that the strength does not depend on the number of hydrogens in the formula
e.g. H 3 PO 4 is a weak acid while HCl is a strong acid
Organic Acids contain the carboxyl group -COOH
They are generally weak acids.
example: acetic acid
CH 3 COOH + H 2 O = H 3 O 1+ + CH 3 COO 1-
where the equilibrium is far to the left i.e. many molecules, few ions
only the hydrogen in the carboxyl group is ionizable
figure 15-7 page 461
- Aqueous
Solutions of Bases
usual bases are metal cations and OH 1- anions - ionic compounds, therefore, dissociation
alkaline - definition
one common base that is not ionic is ammonia, NH 3, which undergoes ionization
NH 3 + H 2 O = NH 4 1+ + OH 1-
- Strength
of Bases
strength depends on the extent of ionization - how many hydroxides it creates in solution
a strong base would be KOH
strong bases are strong electrolytes
table 15-4 page 461
bases that are slightly soluble produce few hydroxide ions and are weak bases
e.g. copper (II) hydroxide
figure 15-8 page 462
the higher the concentration of hydroxide ions in solution the stronger the base
ammonia is highly soluble but a weak base because it produces few hydroxide ions in solution
organic compounds with nitrogen are also weak bases
e.g. aniline C 6 H 5 NH 2 where it picks up a hydrogen ion from water to produce hydroxide ions
Homework: 15.1
- Aqueous
Solutions of Acids
Arrhenius' theory required aqueous solutions
Some substances behaved like acids or bases without water
Other theories arose to account for these
- Bronsted-Lowry
Acids and Bases
Bronsted-Lowry acid - definition
a hydrogen ion is a proton
e.g. HCl + NH 3 ---> NH 4 1+ + Cl 1-
The hydrogen chloride donates a proton to the ammonia and so behaves like a Bronsted acid.
The same happens with the reaction of hydrogen chloride and water.
Water behaves like a Bronsted acid when it reacts with ammonia.
Bronsted Lowry base - definition
Bronsted-Lowry acid base reaction - definition
e.g. reaction of hydrogen chloride and ammonia
HCl + NH 3 ---> NH 4 1+ + Cl 1-
- Monoprotic
and Polyprotic Acids
monoprotic acid - definition
perchloric acid, HClO 3
nitric acid, HNO 3
hydrochloric acid, HCl
polyprotic acid - definition
sulfuric acid, H 2 SO 4
phosphoric acid, H 3 PO 4
Polyprotic acids lose their hydrogen one at a time, in stages
diprotic acid - definition
triprotic acid - definition
Most polyprotic acids have the greatest concentration of ions in the first ionization and each subsequent ionization in the process produces fewer ions
- Monoprotic
and Polyprotic Acids
- Lewis Acids
and Bases
Both previous theories assume the presence of hydrogen ions.
Lewis based his theory on bonding and structure, whether the substance contains hydrogen ions or not.
This is the same person whose name is associated with Lews Dot Structures.
Lewis Acid - definition
Broadest of the definitions.
A hydrogen ion can be a Lewis acid by accepting an electron pair to form a covalent bond.
e.g. page 467 silver ion
Can include any atom with three valence electrons that can form three covalent bonds
Table 15-5 page 468
Lewis Base - definition
An anion with an electron pair it can donate can be a Lewis base.
page 468 fluoride ion
Homework: 15.2
Use Bronsted-Lowry defintion to describe reactions in this section
- Conjugate Acids
and Bases
A substance that gives up a proton and subsequently accept a proton if there is a reverse reaction or something similar.
Conjugate Base - definition
page 469
Conjugate acid-base pairs are the acid and its conjugate base and the base and its conjugate acid.
- Strength
of Conjugate Acids and Bases
The extent of the reaction between a Bronsted-Lowry acid and base depends on the relative stengths of the acids and bases involved. i.e. How far the forward reaction goes before equilibrium depends on the strength of the acid and base.
page 470 HCl + water
HCl gives up its proton readily -- strong acid -- so the chloride ion will not accept a proton readily; the stronger the acid the weaker its conjugate base; the strong the base, the weaker its conjugate acid.
page 470 perchloric acid + water
comparing the ability of perchloric acid v hydronium ion is ability to donate a proton; evidence of concentrations done by experimentation.
page 470 acetic acid + water
The stronger acid and base reaction will be the favored reaction i.e. you will have more of the weaker acid and base in solution than the stronger.
Table 15-6 page 471
Mixing a very strong acid with a very strong conjugate base could be dangerous.
- Strength
of Conjugate Acids and Bases
- Amphoteric
Compounds
Amphoteric - definition
page 472 sulfuric acid + water
page 472 ammonia + water
The strength of the substance it is reacting with determines if the amphoteric substance will act as either an acid or a base.
- -OH in
a Molecule
Molecular compounds containing an -OH group can be acidic or amphoteric.
The hydroxyl group is -OH
A compound with a hydroxyl group must be able to donate the hydrogen of that group to a water molecule to be an acid. The more polar the bond between the O--H the more likely this will happen. When the -OH is attached to a nonmetal from the upper right of the periodic table it has a polar bond that allow the hydrogen from the hydroxyl group to be donated to water.
This includes all oxyacids such as sulfuric, phosphoric, etc.
Figure 15-12 page 472 oxyacids of chlorine
More oxygen atoms attached to the chlorine, the more polar the bond between the O-H will be and the more likely the compound will donate the hydrogen of the hydroxyl group.
page 473 Compounds containing chromium and -OH group
Figure 15-13 page 473
- -OH in
a Molecule
- Neutralization
Reactions
Acid + base ---> salt + water
Acid properties usually cancel basic properties to yield neutral substance (salt) in water.
sodium bicarbonate + tartaric acid in baking powder
antacid
- Strong
Acid-Strong Base Neutralization
HCl is a strong acid
NaOH is a strong base
HCl + H 2 O ---> H 3 O 1+ + Cl 1-
NaOH (aq) ---> Na + (aq) + OH 1- (aq)
Mixing the two solutions produces an ionic equation that can be reduced to the reaction between the hydronium ion and the hydroxide ion to produce water.
Neutralization - definition
Salt - definition
- Acid Rain
Nonmetal oxides that are the result of industrial processes can react with moisture in the air to produce acids. These acids can mix with rain/snow and produce acid rain.
e.g. SO 3(g) + H 2 O (l) ---> H 2 SO 4(aq)
which when it comes in contact with marble gives the reaction
CaCO 3(s) + 2 H 3 O (1) + ---> Ca 2+ (aq) + CO 2(g) + 3 H 2 O (l)
Figure 15-15 page 475
Homework: 15.3
end of notes
- Strong
Acid-Strong Base Neutralization
Binary acid is an acid that contains only two different elements: hydrogen and one of the more electronegative elements. back
An oxyacid is an acid that is a compound of hydrogen, oxygen, and a thir element, usually a nonmetal. back
An Arrhenius acid is a chemical compund that increases the concentration of hydrogen ions, in aqueous solution. back
An Arrhenius base is a susbtance that increases the concentration of hydroxide ions in aqueous solution. back
A strong acid is one that ionizes completely in aqueous solution. back
A weak acid is an acid that is a weak electrolyte. back
Alkaline is used to describe a solution of a base that completely dissociates in water to yield aqueous hydroxide ions. back
A Bronsted-Lowry acid is a molecule or ion that is a proton donor. back
A Bronsted-Lowry base is a molecule or ion that is a proton acceptor. back
In a Bronsted-Lowry acid base reaction protons are transferred from one reactant (the acid) to another (the base). back
A monoprotic acid is an acid that can donate only one proton (hydrogen ion) permolecule. back
A polyprotic acid is an acid that can donate more than one proton per molecule. back
A diprotic acid is an acid that can donate two protons per molecule. back
A triprotic acid is an acid that can donate three protons per molecule. back
A Lewis acid is an atom, ion, or molecule that accepts an electron pair to form a covalent bond. back
A Lewis base is an atom, ion, or molecule that donates an electron pair to form a covalent bond. back
A Lewis acid base reaction is the formation of one or more covalent bonds between an electron pair donor and an electron pair acceptor. back
A conjugate base is the species that remains after a Bronted-Lowry acid has given up a proton. back
A conjugate acid is the species that is formed when a Bronsted-Lowry base gains a proton. back
Amphoteric describes any species that can react as either an acid or a base. back
Neutralization is the reaction of hydronium ions and hydroxide ions to form water molecules. back
A salt is an ionic compound composed of a cation from a base and an anion from an acid. back