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ACIDS & BASES. BACKGROUND. 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.

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ACIDS & BASES


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slide2

BACKGROUND

  • 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.
slide3

ACIDS -

A class of compounds whose water solutions taste sour, turn blue litmus to red, and react with bases to form salts.

slide4

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.
slide5

ACIDS

  • Examples of acids:
  • Vinegar
  • Lemon Juice
  • Soft Drink
  • Battery Acid
  • Stomach Acid
  • Apple Juice
  • Black Tea
slide6

STRONG AND WEAK ACIDS

  • 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

  • chloric acid, HClO3
  • hydorbromic acid, HBr
  • hydorchloric acid, HCl
  • sulfuric acid, H2SO4
  • nitric acid, HNO3
  • acetic acid, Ch3COOH
  • boric acid, H3BO3
  • hydorfluoric acid, HF
  • phosphoric acid, H3PO4
  • sufurous acid, H2So3
slide7

BASES -

A class of compounds that taste bitter, feel slippery in water solution, turn red litmus to blue, and react with acids to form salts.

slide8

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.
slide9

BASES

  • Examples of bases:
  • Detergent
  • Baking Soda
  • Drain Cleaner
  • Ammonia
  • Soaps (hand, dish)
  • Antacid
slide10

STRONG AND WEAK BASES

  • Strong Bases – any base that dissociates completely.
  • Weak Bases – any base that dissociates only partially in aqueous solution.

Strong Bases

Weak Bases

  • barium hydroxide, Ba(OH)2
  • calcium hydroxide, Ca(OH)2
  • potassium hydroxide, KOH
  • sodium hydroxide, NaOH
  • trisodium phosphate, Na3PO4
  • ammonia, NH3
  • aniline, C6H5NH2
  • potassium carbonate,K2CO3
  • sodium carbonate, Na2CO3
  • trimethylamine, (CH3)3N
slide11

NEUTRAL

  • 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
slide12

DETERMINING ACIDS & BASES

  • Red litmus paper
  • Blue litmus paper
  • pH
  • Red Cabbage Juice
slide13

RED

BLUE

LITMUS PAPER

&

  • 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
slide14

pH -

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
slide15

RED CABBAGE JUICE

  • 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
slide16

ACID-BASE THEORIES

There are three common acid-base theories:

  • the Arrhenius theory
  • the Bronsted-Lowry theory
  • the Lewis theory
slide17

Arrhenius 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 H+ + Cl-
  • NaOH Na+ + OH-
slide18

BRONSTED-LOWRY THEORY

  • 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 H3O+ + Cl-

acid

base

Lowry

Bronsted

slide19

LEWIS THEORY

  • 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.
slide20

SUMMARY OF ACID-BASE THEORIES

THEORY

ACID DEFINITION

BASE DEFINITION

Any substance which releases H+ ion in water solution.

Any substance which releases OH- ions in water solution.

Arrhenius Theory

Bronsted-Lowry Theory

Any substance which donates a proton.

Any substance which accepts a proton.

Lewis Theory

Any substance which can accept an electron pair.

Any substance which can donate an electron pair.

slide21

IN YOUR BODY

  • 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.
slide22

DNA

  • 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.
slide23

SUMMARY

  • 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.
slide24

SUMMARY

  • 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.
slide25

????QUESTIONS????

  • ______ _____ in the 1660s, discovered that certain plant extract could be used to distinguish between acids and bases.
  • Name an example of an acid that was mentioned on one of the slides.
  • Name an example of a base that was mentioned on one of the slides.
  • The three common acid-base theories are the Lewis theory, ________ theory, and the Bronsted-Lowery theory.
  • True or False. DNA is a weak acid, and it is weaker than phosphoric acid.
slide26

!!!ANSWERS!!!

  • Robert Boyle
  • 2. Vinegar, Lemon Juice, Soft Drink, Battery Acid, Stomach Acid, Apple Juice, or Black Tea.
  • Detergent, Baking Soda, Drain Cleaner, Ammonia, Soaps (hand, dish), or Antacid.
  • Arrhenius
  • False. It is stronger that phosphoric acid.
slide27

BIBLIOGRAPHY PAGE

  • 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.