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Acids and Bases

Acids and Bases. (p. 256-261, 264-265). Acids. Taste sour. USES OF ACIDS. Citric acid and ascorbic acid (Vitamin C) are found in orange juice Carbonic acid and phosphoric acid give a “bite” to soft drinks Acids in your stomach aid in digestion

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Acids and Bases

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  1. Acids and Bases (p. 256-261, 264-265)

  2. Acids • Taste sour

  3. USES OF ACIDS • Citric acid and ascorbic acid (Vitamin C) are found in orange juice • Carbonic acid and phosphoric acid give a “bite” to soft drinks • Acids in your stomach aid in digestion • Sulfuric acid is the most widely used industrial acid in the world. It is used in making metals, paper, paints, and fertilizers.

  4. Some Properties of Acids • Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) • Taste sour • Corrode metals • Electrolytes • React with bases to form a salt and water (neutralization reaction) • pH is less than 7 • Turns blue litmus paper to red “Blue to Red A-CID”

  5. Acids • Ionize when dissolved in water (they dissociate (break apart) into their ions; +, -). • This allows the water to conduct electricity (which means they are electrolytes). • Ex- HCl is an acid…when placed in water, it becomes H+ and Cl-

  6. Do you remember what an ion is? An ion is an atom that has lost or gained an electron giving it a positive (+) or negative (-) charge.

  7. Acids • Acids produce Hydrogen Cations • Therefore, the formula for an acid must have H in it (usually it will be at the beginning of the chemical formula only) • Ex. HCl, H2SO4

  8. Acids Most acids produce H+ (H3O+) in water • The H+ will attach to H2O to form Hydronium ions (H3O+) • Acids produce H3O+ in water

  9. Strong vs. Weak AcidsSee Table on p. 258 Weak Acid • Don’t ionize completely (don’t produce as many ions) • CH3COOH + H2O  H3O+ + CH3COO- • weak electrolytes Strong Acid • Ionize completely • HNO3+ H2O  H3O+ + NO3- • strong electrolytes • (can conduct electricity well)

  10. BASES • Taste Bitter and Soapy • Feel Slippery

  11. Some bases contain hydroxide ions, OH- , in their formulas, others don’t. NaOH sodium hydroxide lye KOH potassium hydroxide liquid soap Ba(OH)2 barium hydroxide stabilizer for plastics Mg(OH)2 magnesium hydroxide “MOM” Milk of magnesia Al(OH)3 aluminum hydroxide Maalox (antacid)

  12. Bases • Those that don’t have OH in the formula will react with water to produce OH- ions. • All produce hydroxide ions, OH- , in water & conduct electricity (electrolytes).

  13. Strong vs. Weak Bases Weak Bases • Don’t have OH in their formula • (ex-NH3) • ionize in water to produce OH- (water gives up an H), but doesn’t ionize completely • ex. NH3 + H2O  NH4++ OH- • Weak electrolyte Strong Bases • Have OH and a metal atom in their formula • (ex-NaOH) • Dissociate (break apart) in water to give: OH- & metal ion • ex. NaOH OH- + Na+ • Strong electrolyte

  14. Some Properties of Bases • Produce OH- ions in water • Taste bitter, chalky • Are electrolytes • Feel soapy, slippery • React with acids to form salts and water (neutralization reactions) • pH greater than 7 • Turns red litmus paper to blue “Basic Blue”

  15. Uses of Bases • Bases are used in soaps (remember, bases are slippery) • Bases are used to make paper, in oven cleaners, and to unclog drains • Ammonia is a base and is used in many household cleaners

  16. NEUTRAL The pH Scale ACID BASE 0 1 2 3 4 5 67 8 9 10 11 12 13 14 Let’s get pHunky! Acid and Base strength is measured ona scale that ranges from 0 to 14.

  17. The pH scale is a way of expressing the strength of acids and bases. Under 7 = acid 7 = neutralOver 7 = baseNote: Stronger acids have lower numbers & stronger bases have higher numbers

  18. What does “pH” mean? • pH stands for “power of hydronium ion” • A strong acid (low pH..2 or 3) has a high amount of Hydronium ions (H3 O+ ) • A weak acid (higher pH…5 or 6) has a low amount of Hydronium ions (H3 O+ )

  19. Detecting Acids and Bases • You can detect an acid using an indicator. • INDICATOR - A substance that changes color in the presence of an acid or a base.

  20. INDICATORS • Litmus paper is an indicator • An acid turns blue litmus paper red • A base turns red litmus paperblue

  21. pH testing • There are several ways to test pH • Blue litmus paper (red = acid) • Red litmus paper (blue = basic) • pH paper (multi-colored) • pH meter (7 is neutral, <7 acid, >7 base) • Universal indicator (multi-colored) • Indicators like phenolphthalein • Natural indicators like red cabbage, radishes

  22. Paper testing

  23. Neutralization Reaction • When an acid and a base are combined a salt and water are formed. • Ex. HCl + NaOH → NaCl + H2O (acid) (base) (salt) (water) The pH of the salt should be close to neutral (pH 7)

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