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The “Basics” of Acids and Bases

The “Basics” of Acids and Bases. Before Beginning Video. Reminder: Are your Acid Rain Antacid Reading Questions Done (Pages 33-34)? Procure a Writing Utensil Turn in Your Unit 3 Packets to Page 35. Acids & Bases are all around us. Alkaline batteries use KOH (a base).

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The “Basics” of Acids and Bases

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  1. The “Basics” of Acids and Bases

  2. Before Beginning Video • Reminder: Are your Acid Rain Antacid Reading Questions Done (Pages 33-34)? • Procure a Writing Utensil • Turn in Your Unit 3 Packets to Page 35

  3. Acids & Bases are all around us Alkaline batteries use KOH (a base) Car batteries use concentrated sulfuric acid!

  4. Acids & Bases are all around us Drano uses concentrated sodium hydroxide!

  5. Acids & Bases are all around us Bases are used to break down hair! Nair uses Calcium Hydroxide Hair dyes use ammonia

  6. Dangers of Acids & Bases • Most acids are dilute or weak enough to be fairly harmless • We eat some acids • Vinegar is acetic acid • Citrus fruits contain citric acid and vitamin C (ascorbic acid) • Our stomach “gastric juices” are HCl • pH can vary from 1 to 3 • can get to as concentrated as 0.15M HCl

  7. Dangers of Acids & Bases • Concentrated HCl – exposure to it for a minute or less if rinsed and dried thoroughly afterward will probably result in no serious effects. • Nitric Acid attacks proteins, so exposure would turn your skin yellow and cause it to peel from damage. • Sulfuric Acid – can severely burn your skin. • Hydrofluoric Acid can be fatal if breathed in or even with a small spill on your skin.

  8. What is an acid or base? • Arrhenius Definition • Acids dissociate in water to produce hydrogen ions • HCl  H+ + Cl- • Bases dissociate in water to produce hydroxide ions • KOH  K+ + OH-

  9. What is an acid or base? • Bronsted-Lowry Definition • Acids are proton donors • H+ is a proton • HCl  H+ + Cl- • HCl + H2O  Cl- + H3O+ • Bases are proton acceptors • OH- + HCl  H2O + Cl- • NH3 + HNO3 NH4+ + NO3-

  10. Bronsted-Lowry NH3 NH4+ C2H3O2- CH3CO2H The Acid-Base Umbrella Arrhenius HCl KOH H2SO4 Ba(OH)2 HNO3 NaOH

  11. What about water? • Water is amphiprotic • can behave as acid or base • When water gives up a hydrogen ion, it is ______ • Water as an acid: H2O + CO3-2 OH- + HCO3- • When water accepts a hydrogen ion, it is ________: Water as a base H2O + HCl  H3O+ + Cl- acidic basic

  12. Learning Check 1 • For each rxn below, label whether water is acting an acid or base H2O + PO4-3 OH- + HPO4-2 H2O + HNO3 NO3- + H3O+ H2O + NH3 OH- + NH4+ Acid Base Acid

  13. Learning Check 1 So, if hydrogen is the positive ion, and it dissolves in water, it is an Arrhenius Acid ! • Beside each of the following, label as AA,AB, BA, or BB HNO3KOHCO3-2HC2H3O2NH4+ AA Ca(OH)2 H2SO4 NH3 AB AB AA BB BB AA So, if hydroxide is the negative ion, and it dissolves in water, it is an Arrhenius Base ! BA So, if something has a negative charge, it would probably behave as a base!

  14. Neutralization Reactions • Occurs when an acid and base are mixed • Hydronium (H+) combines with hydroxide (OH-)

  15. Neutralization Reactions • If equal amounts are mixed, the final solution will no longer have properties of acid or base • Examples: • When pools get too acidic, a base is added to bring up the pH levels • If strong acid is spilled in lab, add baking soda • Antacid is taken for a stomach ulcer

  16. Neutralization Reactions • An acid-base titration is a reaction where the amount of acid needed to neutralize a base is measured • An indicator is often used to tell when neutralization has been reached. This is called the equivalence point. • The pH at which an indicator changes color is called the endpoint. • An indicator should be chosen whose endpoint is at the equivalence point for the reaction. How do I know when it is neutralized ?

  17. Indicators and their Endpoints Litmus has an endpoint of 7 What is the endpoint for litmus?

  18. Acid-Base Titration (Neutralization)

  19. Indicators and their Endpoints Phenolphthalein has an endpoint of 8 What is the endpoint for phenolphthalein?

  20. Neutralization Reactions • Neutralization rxns are • Products are always water and a salt H2SO4(aq) + NaOH(aq)  Phosphoric Acid(aq) + Magnesium hydroxide(aq) Double Replacement Rxns

  21. Measuring the Strength of Acids • The strength of an acid is determined by the concentration of H+ ions present • Strong acids completely dissociate in water, while weak acids only partially dissociate. • The higher the concentration of H+ ions, the stronger the acid • Nitric, Hydrochloric, & Sulfuric Acids are strong acids

  22. Measuring the Strength of Acids • The pH Scale • Ranges from ___________ • ___ is neutral (equal amount of H+ and OH-) • pH lower than 7 = ______ • pH higher than 7 = _____ • The lower the pH, the __________ the acid. 1-14 7 acidic basic stronger

  23. Measuring the Strength of Acids • The pH Scale • pH is a measure of the concentration of H+ ions • pH = -log[H+] I thought we said high H+ concentrations were strong acids Which one of those is the highest? Those are weird looking numbers ConcentrationlogpH 1 x 10-7 1 x 10-3 1 x 10-9 -7 7 How can strong acids have pH of 1 if they have high H+ amounts? -3 3 -9 9

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