Transcript ACID - SchoolNotes

• Acid and base are terms used by chemists to categorize
chemicals according to their pH.
•An acid is generally considered to be any material that gives
up a hydrogen ion in solution,
• While a base is any material that creates a hydroxide ion in
solution.
•Many of these acids and bases are familiar in everyday life.
A class of compounds whose water
solutions taste sour, turn blue litmus to
red, and react with bases to form salts.
Acids produce solutions that:
• Taste sour
• Turn blue litmus paper red
• Conduct electricity
• react with metals to liberate a hydrogen gas
• are corrosive (acid rain)
• lose the above properties when reacted with a base.
Examples of acids:
• Vinegar
• Lemon Juice
• Soft Drink
• Battery Acid
• Stomach Acid
• Apple Juice
• Black Tea
• Strong Acids – any acid that dissociates completely in aqueous solution.
• Weak Acids – any acid that dissociates only partially in aqueous solution.
Strong Acids
Weak Acids
1. chloric acid, HClO3
1. acetic acid, Ch3COOH
2. hydorbromic acid, HBr
2. boric acid, H3BO3
3. hydorchloric acid, HCl
3. hydorfluoric acid, HF
4. sulfuric acid, H2SO4
4. phosphoric acid, H3PO4
5. nitric acid, HNO3
5. sufurous acid, H2So3
A class of compounds that taste
bitter, feel slippery in water solution,
turn red litmus to blue, and react with
acids to form salts.
Bases produce solutions that:
• taste bitter
• turn red litmus blue
• conduct electricity
• feel slippery
• are corrosive (basic solution in glass container)
• lose the above properties when reacted with an acid.
Examples of bases:
• Detergent
• Baking Soda
• Drain Cleaner
• Ammonia
• Soaps (hand, dish)
• Antacid
• Strong Bases – any base that dissociates completely.
• Weak Bases – any base that dissociates only partially in aqueous solution.
Strong Bases
Weak Bases
1. barium hydroxide, Ba(OH)2
1. ammonia, NH3
2. calcium hydroxide, Ca(OH)2
2. aniline, C6H5NH2
3. potassium hydroxide, KOH
3. potassium carbonate,K2CO3
4. sodium hydroxide, NaOH
4. sodium carbonate, Na2CO3
5. trisodium phosphate, Na3PO4
5. trimethylamine, (CH3)3N
• These are items that are neither acids or
bases.
• Neutral items will turn blue and red litmus
paper green.
• The main example of a neutral item is:
Pure Water
• Red litmus paper
• Blue litmus paper
• pH
• Red Cabbage Juice
•Robert Boyle discovered litmus paper
•certain plant extracts, such as litmus, can be
used to distinguish acids from bases.
• blue and red litmus paper turn red when
dipped in an acid
• red and blue litmus paper turn blue when
exposed to a base
the negative logarithm of the
hydronium ion concentration of
an aqueous solution; used to
express acidity.
• pH is the measure of the acidity or
basicity of a solution.
• The pH scale ranges from 1 to 14
• 1 through 6 being acidic
• 7 is considered neutral
• 8 through 14 being basic
• red cabbage can be used as an acid/base
indicator
• after boiling the red cabbage, pour a small
amount of the juice into a small sample of a
substance your checking
• the juice will turn blue if the substance is a
base
• the juice will turn red if the substance is an
acid
There are three common acid-base theories:
• the Arrhenius theory
• the Bronsted-Lowry theory
• the Lewis theory
• Svante Arrhenius was a Swedish chemist.
• In 1887, he published a paper concerning acids and bases.
• He concluded that solutions with acids and bases in them released
particles when dissolved.
• He concluded that acids were substance which separated (ionized) in
water solution to produce hydrogen ions (H+, or free protons).
• He also believed that bases were substance which ionized to produce
hydroxide ions (OH-) in water solution.
• HCl
• NaOH
H+ + ClNa+ + OH-
• T. M. Lowry was an English scientist, while J. N. Bronsted
was a Danish scientist.
• In 1923, they independently proposed a new definition of
the terms acid and base.
• They stated that in a chemical reaction, any substance
which donates a proton is an acid and any substance which
accepts a proton is a base.
• When hydrogen chloride gas is dissolved in water, ions are
formed:
• HCl + H2O
acid
H3O+ + Cl-
base
Lowry
Bronsted
• Gilbert Newton Lewis was and American chemist.
• In 1923, proposed an even broader definition of acids and
bases.
• Lewis focused on electron transfer instead of proton transfer.
• He defined and acid as an electron-pair acceptor, and a base as
an electron-pair donor.
• This definition applies to solutions and reactions which do not
even involve hydrogen or hydrogen ions.
THEORY
ACID DEFINITION
Arrhenius
Theory
Any substance which
releases H+ ion in
water solution.
Any substance which
releases OH- ions in
water solution.
Any substance which
donates a proton.
Any substance which
accepts a proton.
Bronsted-Lowry
Theory
Lewis
Theory
Any substance which can
accept an electron pair.
BASE DEFINITION
Any substance which
can donate an
electron pair.
• Proteins
in your hair, nails, cell membranes,
and other parts of you body consist of amino
acids.
• Enzymes that catalyze reactions in your body
are composed of amino acids.
• Hydrochloric acid is in your stomach to aid in
the digestion of food.
• Organic bases are major components of DNA
and products of the digestion of proteins.
• DNA contains thousands of sites where
H+ ion transfer can take place
• Therefore DNA fits the definition of a
Bronsted acid.
• DNA is a weak acid, but it is stronger
than phosphoric acid.
• ACID - A class of compounds whose water solutions
taste sour, turn blue litmus to red, and react with bases to
form salts.
• BASE - A class of compounds that taste bitter, feel
slippery in water solution, turn red litmus to blue, and
react with acids to form salts.
• NEUTRAL - These are items that are neither acids or
bases.
There are 4 main ways to determine if a substance is and
acid or a base. They are: Red litmus paper, Blue litmus
paper, pH, and Red Cabbage Juice.
• There are 3 common acid-base theories: the Arrhenius
theory, the Bronsted-Lowry theory, and the Lewis
theory.
• The body is a sea of acids and bases.
• DNA is an acid based on Bronsted’s definition of an
acid.
1. ______ _____ in the 1660s, discovered that certain plant
extract could be used to distinguish between acids and bases.
2. Name an example of an acid that was mentioned on one of the
slides.
3. Name an example of a base that was mentioned on one of the
slides.
4. The three common acid-base theories are the Lewis theory,
________ theory, and the Bronsted-Lowery theory.
5. True or False. DNA is a weak acid, and it is weaker than
phosphoric acid.
1. Robert Boyle
2. Vinegar, Lemon Juice, Soft Drink, Battery Acid, Stomach Acid,
Apple Juice, or Black Tea.
3.
Detergent, Baking Soda, Drain Cleaner, Ammonia, Soaps
(hand, dish), or Antacid.
4.
Arrhenius
5.
False. It is stronger that phosphoric acid.
• Background information on acids and bases.
<http://educ.queensu.ca/~science/main/concept/chem/c10/C10CDMJ1.htm>
• Acids and Bases. <http://www.bookrags.com/research/acids-and-bases-woc/>
• Acids and bases Lab. <http://www. Scribd.com/doc/2977162/Acids-and-Bases-Lab/>
• Smoot, Robert C.; Price, Jack S.; Smith, Richard G. Chemistry A Modern Course.
Chapter 24, Acids, Bases, and Salts.
• Holt, Rinehart, and Winston, Inc. Chemistry Visualizing Matter. Chapter 13, Acids and
Bases.