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Do Now

Learn about the properties of acids and bases, examples, strengths, and acid-base theories. Explore pH scale, red cabbage juice indicator, and common misconceptions.

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Do Now

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  1. Do Now • Sit SILENTLY and answer the following questions in your notes… • List 5 things you eat that are sour. Do you think these are made of acids or bases? • List 5 things that you eat that taste bitter. Do you think these are made of acids or bases? • Do you think water is an acid or a base?

  2. ACIDS & BASES BY Mr. Miller

  3. 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.

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

  5. 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.

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

  7. 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 Note: aqueous solution is any solution where water is the solvent.

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

  9. 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.

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

  11. 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

  12. 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

  13. DETERMINING ACIDS & BASES • Red litmus paper • Blue litmus paper • pH • Red Cabbage Juice

  14. 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

  15. 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

  16. 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

  17. ACID-BASE THEORIES There are three common acid-base theories: • the Arrhenius theory • the Bronsted-Lowry theory • the Lewis theory

  18. 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-

  19. 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

  20. 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.

  21. 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.

  22. 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.

  23. Catalysts • A substance that increases the rate of reactivity of a chemical reaction without itself undergoing a chemical change. • Elephant Toothpaste

  24. 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.

  25. 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.

  26. 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.

  27. Exit Ticket!!! • ______ _____ 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.

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