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Acids & Bases

Acids & Bases. Standards: Chem 5a. Students know the observable properties of acids, bases, and salt solutions. Chem 5c. Students know strong acids and bases fully dissociate and weak acids and bases partially dissociate. What are acids?. Some are dangerous and can burn your skin

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Acids & Bases

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  1. Acids & Bases Standards: Chem 5a. Students know the observable properties of acids, bases, and salt solutions. Chem 5c. Students know strong acids and bases fully dissociate and weak acids and bases partially dissociate.

  2. What are acids? • Some are dangerous and can burn your skin • Some are safe to eat and drink • Stomach acid helps digest food

  3. Properties of Acids • Acids can be solids, liquids, or gases • A group of compounds which behave similarly • All have pH below 7 • Turn Litmus paper RED • In an acidic solution, [H3O+]>[OH-] • All donate H+ ions in aqueous solution water HCl H+(aq) + Cl- (aq)

  4. Properties of Acids • Acids are generally sour in taste • Strong acids and some concentrated weak acids are corrosive and can cause severe burns. • Generally when you see a compound with “H” in it, i.e. HCl, HCN, it indicates that compound is an acid • In dilute concentrations, acids are responsible for the sour taste in lemons, limes, vinegar & other substances

  5. Examples of Strong Acids • Strong acids FULLY dissociate into H+ and an anion (negative ion) when they are mixed with H2O • HCl - hydrochloric acid • HI - hydroiodic acid • HNO3 - nitric acid • HClO4 - perchloric acid • HBr - hydrobromic acid • H2SO4 - sulfuric acid

  6. Examples of Weak Acids • Weak acids do NOT fully dissociate; they are partially ionized in their solutions • CH3COOH - acetic acid, aka vinegar • HF - hydrofluoric acid • HCOOH - formic acid, found in venom of bee & ant stings

  7. Acid Reactions • Acid + Base  Salt + Water • Acid + Metal Salt + Hydrogen • Acid + Carbonate  Salt + Water + Carbon Dioxide • Hydrochloric acids (HCl) form CHLORIDE salts • Nitric acid (HNO3) forms NITRATE salts • Sulfuric acid (H2SO4) forms SULFATE salts

  8. What are Bases (Alkalis)? • In our home we often use bases to clean things. Ex: Bleach and toothpaste

  9. Properties of Bases • Generally when you see a compound with “OH” in it, i.e. NaOH, KOH, it indicates that compound is a base. OH- = hydroxide • pH greater than 7 • Have bitter taste, feel slippery to the touch • Strong base can also cause serious burns • Turn red litmus paper blue • All donate OH- ions in water • In a basic solution, [H3O+]<[OH-]

  10. Properties of Bases • Example: H2O + NH3 OH- + NH4+ H+ donor (acid) H+ acceptor (base)

  11. Examples of Strong Bases • Strong bases FULLY dissociate into OH- and a cation (positive ion) when they are mixed with H2O • The cations of these strong bases appear in the first & second groups of the periodic table • LiOH - lithium hydroxide • Mg(OH)2 - magnesium hydroxide • NaOH - sodium hydroxide • Ca(OH)2 - calcium hydroxide • KOH - potassium hydroxide • and more..

  12. Examples of Weak Acids • Weak bases do NOT fully dissociate • NH3 • And more…

  13. Learning Check • Describe the solution in each of the following as: 1) acid 2) base or 3)neutral. • A. ______ Soda • B. ______ Soap • C. ______ Coffee • D. ______ Wine • E. ______ Water • F. ______ Grapefruit

  14. Learning Check • Describe the solution in each of the following as: 1) acid 2) base or 3)neutral. • A. _Acid__ Soda • B. _Base__ Soap • C. _Acid__ Coffee • D. _Acid_ Wine • E. _Neutral__ Water • F. _Acid__ Grapefruit

  15. Learning Check • Identify each as characteristic of an A) acid or B) base • A. ____ Sour taste • B. ____ Produces OH- in aqueous solutions • C. ____ Produces H+ in aqueous solutions • D. ____ Feels slippery to the touch

  16. Learning Check • Identify each as characteristic of an A) acid or B) base • A. __A_ Sour taste • B. __B_ Produces OH- in aqueous solutions • C. __A_ Produces H+ in aqueous solutions • D. __B_ Feels slippery to the touch

  17. Salt Solutions • Any ionic compound formed from the reaction between an acid and a base • The reaction between an acid and a base is called a neutralization reaction • Far less corrosive than acids or bases from which they are formed • Examples: • HCl + NaOH NaCl + H2O • HCl + KOH KCl + H2O

  18. Learning Check • Acid, Base or Salt? • A. ______ CaCl2 • B. ______ KOH • C. ______ Ba(OH)2 • D. ______ HBr • E. ______ H2SO4

  19. Learning Check • Acid, Base or Salt? • A. __salt____ CaCl2 • B. __base____ KOH • C. __base____ Ba(OH)2 • D. __acid____ HBr • E. __acid____ H2SO4

  20. pH Scale 7 Acid Base 0 14

  21. pH of common substances

  22. Acid – Base Concentrations 10-1 pH = 3 pH = 11 OH- H3O+ pH = 7 10-7 concentration (moles/L) H3O+ OH- OH- H3O+ 10-14 [H3O+]<[OH-] [H3O+]>[OH-] [H3O+]=[OH-] acidic solution neutral solution basic solution Timberlake, Chemistry 7th Edition, page 332

  23. pH • pH = -log [H+]

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