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Solutions

Solutions. Vodcast 3 Acids and Bases. Properties of acids. Taste sour Strong acids conduct electricity Can be strong or weak electrolytes in aqueous solution. Acids React with Active Metals. Acids react with active metals to form salts and hydrogen gas:

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Solutions

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  1. Solutions Vodcast 3 Acids and Bases

  2. Properties of acids • Taste sour • Strong acids conduct electricity • Can be strong or weak electrolytes in aqueous solution

  3. Acids React with Active Metals • Acids react with active metals to form salts and hydrogen gas: HCl(aq) + Mg(s) → MgCl2(aq) + H2(g)

  4. Acids Affect Indicators • Indicators are weak acids or bases that have a different color from their original acid and base Blue litmus paper turns red in contact with an acid.

  5. Acids have a pH less than 7

  6. Acids Neutralize Bases HCl + KOH → KCl + H2O Neutralization reactions ALWAYS produce a salt and water. • Of course, it takes the right proportion of acid and base to produce a neutral salt

  7. Examples of Acids • Hydrochloric acid, HCl • Nitric Acid, HNO3 • Sulfuric Acid, H2SO4 • Phosphoric Acid, H3PO4 • Acetic Acid, HC2H3O2

  8. Effects of Acid Rain on Marble(calcium carbonate) George Washington: BEFORE George Washington: AFTER

  9. Properties of bases • Feel slippery like soap • Taste bitter • Strong bases conduct electricity • Can be strong or weak electrolytes in aqueous solution

  10. Bases Affect Indicators Red litmus paper turns blue in contact with a base. Phenolphthalein turns purple in a base.

  11. Bases have a pH greater than 7

  12. Bases Neutralize Acids • Milk of Magnesia contains magnesium hydroxide, Mg(OH)2, which neutralizes stomach acid, HCl. 2 HCl + Mg(OH)2 MgCl2 + 2 H2O

  13. Examples of Bases • Sodium hydroxide (lye), NaOH • Potassium hydroxide, KOH • Magnesium hydroxide, Mg(OH)2 • Calcium hydroxide (lime), Ca(OH)2 • Ammonia, NH3

  14. 1. Arrhenius Definition - 1887 • Acids produce hydrogen ions (H+) in aqueous solution. • Bases produce hydroxide ions (OH-) when dissolved in water. • Only hydroxides are bases • NH3 (ammonia) could not be an Arrhenius base.

  15. 2. Brønsted-Lowry - 1923 • Acid is hydrogen-ion donor (H+ or proton); base is hydrogen-ion acceptor. • Acids and bases always come in pairs. • HCl is an acid. • When it dissolves in water, it gives it’s proton to water. • HCl(g) + H2O(l) H3O+ + Cl- • Water is a base; makes hydronium ion.

  16. Why Ammonia is a Base Ammonia can be explained as a base by using Brønsted-Lowry: NH3(aq) + H2O(l)↔ NH41+(aq) + OH1-(aq)

  17. Acids and bases come in pairs • A “conjugate base” is the remainder of the original acid, after it donates it’s hydrogen ion • A “conjugate acid” is the particle formed when the original base gains a hydrogen ion

  18. Acids and bases come in pairs General equation is: • HCl(aq) + H2O(l) ↔ H3O+(aq) + Cl-(aq) Acid + Base ↔ Conjugate acid + Conj. base • NH3 + H2O ↔ NH41+ + OH1- base acid c.a. c.b.

  19. Acids and bases come in pairs • HCl + H2O ↔ H3O1++ Cl1- acid base c.a. c.b. • Amphoteric – a substance that can act as both an acid and base- as water shows

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