Chapter 15.2 “ Acids, Bases, and Salts ”
Properties of Acids <ul><li>They taste  sour  (don’t try this at home). </li></ul><ul><li>They can  conduct electricity . ...
Properties of Acids <ul><li>They have a  pH of less than 7  (more on this concept of pH in a later lesson) </li></ul><ul><...
Acids Affect Indicators, by changing their color Blue litmus paper turns red in contact with an acid  (and red paper stays...
Acids have a pH  less   than 7
Acids React with Active Metals Acids react with active metals to form salts and hydrogen gas: HCl (aq)  + Mg (s)   -> MgCl...
Effects of  Acid Rain  on Marble (marble is calcium  carbonate ) George Washington: BEFORE acid rain George Washington: AF...
Strong vs. Weak <ul><li>When all the molecules of an acid break apart in water to produce hydrogen ions </li></ul><ul><li>...
Sulfuric Acid  = H 2 SO 4 <ul><li>Highest volume production of  any  chemical in the U.S.  (approximately 60 billion pound...
Nitric Acid  = HNO 3 <ul><li>Used in the production of fertilizers </li></ul><ul><li>Used in the production of explosives ...
Hydrochloric Acid  = HCl <ul><li>Used in the “pickling” of steel </li></ul><ul><li>Used to purify magnesium from sea water...
Phosphoric Acid  = H 3 PO 4 <ul><li>A flavoring agent in sodas (adds “tart”) </li></ul><ul><li>Used in the manufacture of ...
Acetic Acid  = HC 2 H 3 O 2  (also called Ethanoic Acid, CH 3 COOH) <ul><li>Used in the manufacture of plastics </li></ul>...
Acids  Neutralize  Bases HCl + NaOH  ->  NaCl + H 2 O - Neutralization reactions ALWAYS produce a salt (which is an  ionic...
Acid and Bases <ul><li>Can water dissociate(break apart)? </li></ul><ul><ul><ul><li>H 2 O  H +   +  OH - </li></ul></ul></...
Properties of Bases   (metallic hydroxides) <ul><li>React with acids  to form water and a salt. </li></ul><ul><li>Taste  b...
Examples of Bases (metallic hydroxides) <ul><li>Sodium hydroxide,  NaOH   ( lye for drain cleaner; soap ) </li></ul><ul><l...
Bases Affect Indicators Red litmus paper turns blue in contact with a base  (and blue paper stays blue). Phenolphthalein t...
Bases have a pH  greater   than 7
Bases Neutralize Acids Milk of Magnesia contains magnesium hydroxide, Mg(OH) 2 , which neutralizes stomach acid, HCl. 2 HC...
The pH concept – from 0 to 14 <ul><li>pH =  pouvoir hydrogene  (Fr.)      “hydrogen power” </li></ul><ul><li>definition:  ...
 
Measuring pH <ul><li>Why measure pH? </li></ul><ul><ul><li>Everyday solutions  we use - everything from swimming pools, so...
How to measure pH with wide-range paper 1. Moisten the pH indicator paper strip with a few drops of solution, by using a s...
Some of the many pH Indicators  and their pH range
Acid-Base Indicators <ul><li>Although useful, there are  limitations   to indicators: </li></ul><ul><ul><li>usually given ...
Acid-Base Indicators <ul><li>A  pH meter  may give more definitive results </li></ul><ul><ul><li>some are  large , others ...
Acid-Base Reactions <ul><li>Acid + Base    Water + Salt </li></ul><ul><li>Properties related to every day: </li></ul><ul>...
Salt <ul><li>A  salt  is an ionic compound that: </li></ul><ul><ul><li>comes from the  anion  of an acid </li></ul></ul><u...
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Chapter 19 acids, bases, and salts probe

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Chapter 19 acids, bases, and salts probe

  1. 1. Chapter 15.2 “ Acids, Bases, and Salts ”
  2. 2. Properties of Acids <ul><li>They taste sour (don’t try this at home). </li></ul><ul><li>They can conduct electricity . </li></ul><ul><ul><li>Can be strong or weak electrolytes in aqueous solution </li></ul></ul><ul><li>React with metals to form H 2 gas. </li></ul><ul><li>Change the color of indicators (for example: blue litmus turns to red). </li></ul><ul><li>React with bases (metallic hydroxides) to form water and a salt. </li></ul>
  3. 3. Properties of Acids <ul><li>They have a pH of less than 7 (more on this concept of pH in a later lesson) </li></ul><ul><li>They react with carbonates and bicarbonates to produce a salt, water, and carbon dioxide gas </li></ul><ul><li>How do you know if a chemical is an acid? </li></ul><ul><ul><li>It usually starts with Hydrogen. </li></ul></ul><ul><ul><li>H Cl, H 2 SO 4 , H NO 3 , etc. (but not water!) </li></ul></ul>
  4. 4. Acids Affect Indicators, by changing their color Blue litmus paper turns red in contact with an acid (and red paper stays red).
  5. 5. Acids have a pH less than 7
  6. 6. Acids React with Active Metals Acids react with active metals to form salts and hydrogen gas: HCl (aq) + Mg (s) -> MgCl 2(aq) + H 2(g) This is a single-replacement reaction
  7. 7. Effects of Acid Rain on Marble (marble is calcium carbonate ) George Washington: BEFORE acid rain George Washington: AFTER acid rain
  8. 8. Strong vs. Weak <ul><li>When all the molecules of an acid break apart in water to produce hydrogen ions </li></ul><ul><li>When few molecules of an acid break apart in water to produce hydrogen ions </li></ul>
  9. 9. Sulfuric Acid = H 2 SO 4 <ul><li>Highest volume production of any chemical in the U.S. (approximately 60 billion pounds/year) </li></ul><ul><li>Used in the production of paper </li></ul><ul><li>Used in production of fertilizers </li></ul><ul><li>Used in petroleum refining; auto batteries </li></ul>
  10. 10. Nitric Acid = HNO 3 <ul><li>Used in the production of fertilizers </li></ul><ul><li>Used in the production of explosives </li></ul><ul><li>Nitric acid is a volatile acid – its reactive components evaporate easily </li></ul><ul><li>Stains proteins yellow (including skin!) </li></ul>
  11. 11. Hydrochloric Acid = HCl <ul><li>Used in the “pickling” of steel </li></ul><ul><li>Used to purify magnesium from sea water </li></ul><ul><li>Part of gastric juice, it aids in the digestion of proteins </li></ul><ul><li>Sold commercially as Muriatic acid </li></ul>
  12. 12. Phosphoric Acid = H 3 PO 4 <ul><li>A flavoring agent in sodas (adds “tart”) </li></ul><ul><li>Used in the manufacture of detergents </li></ul><ul><li>Used in the manufacture of fertilizers </li></ul><ul><li>Not a common laboratory reagent </li></ul>
  13. 13. Acetic Acid = HC 2 H 3 O 2 (also called Ethanoic Acid, CH 3 COOH) <ul><li>Used in the manufacture of plastics </li></ul><ul><li>Used in making pharmaceuticals </li></ul><ul><li>Acetic acid is the acid that is present in household vinegar </li></ul>
  14. 14. Acids Neutralize Bases HCl + NaOH -> NaCl + H 2 O - Neutralization reactions ALWAYS produce a salt (which is an ionic compound ) and water. -Of course, it takes the right proportion of acid and base to produce a neutral salt
  15. 15. Acid and Bases <ul><li>Can water dissociate(break apart)? </li></ul><ul><ul><ul><li>H 2 O H + + OH - </li></ul></ul></ul><ul><li>High concentration of H + ions indicate an acidic solution. </li></ul><ul><li>High concentration of OH - ion indicate a basic solution (also called alkaline) </li></ul>
  16. 16. Properties of Bases (metallic hydroxides) <ul><li>React with acids to form water and a salt. </li></ul><ul><li>Taste bitter . </li></ul><ul><li>Feel slippery (don’t try this either). </li></ul><ul><li>Can be strong or weak electrolytes in aqueous solution </li></ul><ul><li>Change the color of indicators (red litmus turns blue). </li></ul>
  17. 17. Examples of Bases (metallic hydroxides) <ul><li>Sodium hydroxide, NaOH ( lye for drain cleaner; soap ) </li></ul><ul><li>Potassium hydroxide, KOH ( alkaline batteries ) </li></ul><ul><li>Calcium hydroxide, Ca(OH) 2 ( lime ; masonry ) </li></ul><ul><li>Magnesium hydroxide, Mg(OH) 2 ( Milk of Magnesia ) </li></ul>
  18. 18. Bases Affect Indicators Red litmus paper turns blue in contact with a base (and blue paper stays blue). Phenolphthalein turns purple in a base.
  19. 19. Bases have a pH greater than 7
  20. 20. Bases Neutralize Acids Milk of Magnesia contains magnesium hydroxide, Mg(OH) 2 , which neutralizes stomach acid, HCl. 2 HCl + Mg(OH) 2 MgCl 2 + 2 H 2 O Magnesium salts can cause diarrhea (thus they are used as a laxative) and may also cause kidney stones.
  21. 21. The pH concept – from 0 to 14 <ul><li>pH = pouvoir hydrogene (Fr.) “hydrogen power” </li></ul><ul><li>definition: pH = -log[H + ] </li></ul><ul><li>in neutral pH = 7 </li></ul><ul><li>in acidic solution=< 7 </li></ul><ul><li>pH < -log(10 -7 ) </li></ul><ul><ul><li>pH < 7 (from 0 to 7 is the acid range) </li></ul></ul><ul><ul><li>in base , pH > 7 (7 to 14 is base range) </li></ul></ul>
  22. 23. Measuring pH <ul><li>Why measure pH? </li></ul><ul><ul><li>Everyday solutions we use - everything from swimming pools, soil conditions for plants, medical diagnosis, soaps and shampoos, etc. </li></ul></ul><ul><li>Sometimes we can use indicators , other times we might need a pH meter </li></ul>
  23. 24. How to measure pH with wide-range paper 1. Moisten the pH indicator paper strip with a few drops of solution, by using a stirring rod. 2.Compare the color to the chart on the vial – then read the pH value.
  24. 25. Some of the many pH Indicators and their pH range
  25. 26. Acid-Base Indicators <ul><li>Although useful, there are limitations to indicators: </li></ul><ul><ul><li>usually given for a certain temperature (25 o C), thus may change at different temperatures </li></ul></ul><ul><ul><li>what if the solution already has a color , like paint? </li></ul></ul><ul><ul><li>the ability of the human eye to distinguish colors is limited </li></ul></ul>
  26. 27. Acid-Base Indicators <ul><li>A pH meter may give more definitive results </li></ul><ul><ul><li>some are large , others portable </li></ul></ul><ul><ul><li>works by measuring the voltage between two electrodes; typically accurate to within 0.01 pH unit of the true pH </li></ul></ul><ul><ul><li>Instruments need to be calibrated </li></ul></ul>
  27. 28. Acid-Base Reactions <ul><li>Acid + Base  Water + Salt </li></ul><ul><li>Properties related to every day: </li></ul><ul><ul><li>antacids depend on neutralization </li></ul></ul><ul><ul><li>farmers adjust the soil pH </li></ul></ul><ul><ul><li>human body kidney stones from insoluble salts </li></ul></ul>
  28. 29. Salt <ul><li>A salt is an ionic compound that: </li></ul><ul><ul><li>comes from the anion of an acid </li></ul></ul><ul><ul><li>comes from the cation of a base </li></ul></ul><ul><ul><li>is formed from a neutralization reaction </li></ul></ul><ul><ul><li>some neutral; others acidic or basic </li></ul></ul>

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