Background Chemistry, Part 1
What is a pH value and what directly affects pH?
Acids
What is an acid? What makes an acid an acid? What properties do acids
have?
Acids can be described by a variety of physical characteristics such
as taste, touch and its reaction with metals. You can also determine
if a solution is acidic by adding an acid-base indicator, which changes
color depending on whether the solution is acidic or basic.
Did you know that you eat acidic food everyday? Food that is acidic
have a sour or tart taste to them. What foods do you eat that taste
sour? Lemons, oranges and grapefruit, also know as citrus fruits, contain
citric acid. It is the citric acid that gives these fruits their sour
taste. What other foods have sour tastes to them? Yogurt and sour cream
contain lactic acid, and vinegar is the common name for acetic acid.
Even the carbonic acid found in soda is a very weak acid.
Depending on the strength of the acid, acids can sting or burn. It
is a similar to the sensation you feel when you have a open sore in
your mouth.
Bronsted-Lowery Definition
According to the Bronsted-Lowery definition, an acid can donate
H+ ions, or protons. There are a variety of substances that donates
protons. Some acids are monoprotic, meaning they can only donate one
proton. Acetic acid (HC2H3O2)
found in vinegar is a type of monoprotic acid. Other acids may be diprotic
or triprotic, donating 2 or 3 protons respectively.
The strength of an acid's reaction to metals depends on how easily
the acid wants to donate the proton. This can depend on the bulkiness
of the acid molecule. You can use vinegar in cooking because it is a
weak acid and does not want to give up its proton easily. Acetic acid's
proton is also surrounded with many carbon, oxygen and other hydrogen
atoms; thus, making the compound bulky. This hinders the reactivity
of the compound. Hydrochloric acid (HCl), however, is not as cluttered
with atoms and is more easily protonated, donating the proton. Therefore,
HCl is a strong acid.
Proceed
to Learn about Bases
