Acids, bases, salts

1. Acids, bases, salts Unit 9 Notes

2. Acids • An acid is a substance that produces H+ or H3O+solution. • Properties of acids: • 1.  Sour taste • 2.  React with certain metals to produce hydrogen gas • 3.  React with carbonates and bicarbonates to produce carbon dioxide gas • 4. Corrode metals • 5. React with bases to form a salt and water • 6. pH is less than 7 • 7. Turns blue litmus paper to red “Blue to Red A-CID” • 8. Electrolytes- conduct electricity because of ions

3. Rules for naming acids#1: Acids that do not contain oxygenHA Examples: Formula not in water in water HCl hydrogen chloride hydrochloric acid H2S hydrogen sulfide hydrosulfuric acid HCN hydrogen cyanide hydrocyanic acid

4. Rules for naming acids#2: Acids that contain oxygenHAOx

5. Examples: • Formulasalt/gas Formula aqueous • HNO2 hydrogen nitrite HNO2 (aq) nitrous acid • HNO3 hydrogen nitrate HNO3 (aq) nitric acid • H2SO3 hydrogen sulfite H2SO3 (aq) sulfurous acid • H2SO4 hydrogen sulfate H2SO4 (aq) sulfuric acid • H2CO3 hydrogen carbonate H2CO3 (aq) carbonic acid RULES FOR NAMING ACIDS

6. PRACTICE PROBLEMS • GIVE THE FORMULA FOR THE NAME OR THE NAME FOR THE FORMULA • H2S H2SO3 (aq) HF (aq) • HClO2 HIO HNO2 • H2SO4 (aq) HI (aq) H2C2O4 (aq) • Acetic Acid nitrous acid iodic acid

7. COMMON ACIDS AND USES • Acid  Formula  Where found • 1.  Hydrochloric HCl stomach, cleaning supplies • 2.  Sulfuric H2SO4 car batteries, fertilizer • 3.  Nitric HNO3 explosives, fertilizer • 4.  Phosphoric H3PO4 detergents, fertilizers • 5.  Carbonic H2CO3 soda (carbonated) • 6.  Ascorbic H2C2H6O6 vitamin C (fruits, vegetables) • 7.  Acetylsalicylic HOOC-C6H4-OOCCH3 aspirin • 8.  acetic CH3COOH vinegar

8. Strong and weak acids • The most widely used chemical in the world is sulfuric acid. • It can cause severe burns because it is a dehydrating agent. • This means that takes all the water out of materials, including skin. • A strong acid completely ionizes (breaks apart) in water and releases a lot of H+. Example: sulfuric acid (battery acid) • A weak acid only partially breaks down in water, so it doesn’t release much H+. Example: acetic acid (vinegar)

9. Bases • A base is a substance that produces OH- solution. • Properties of bases: • Tastes bitter, chalky • Are electrolytes • Feel soapy, slippery • React with acids to form salts and water • pH greater than 7 • Turns red litmus paper to blue “Basic Blue”

10. Common Bases and uses • Base Formula  Where found • 1.  Sodium hydroxide NaOH soap, lye, drain cleaner • 2.  Potassium hydroxide KOH liquid soap • 3.  Barium hydroxide Ba(OH)2 stabilizer for plastics • 4.  Magnesium hydroxide Mg(OH)2 laxative, antacid • 5.  Calcium hydroxide Ca(OH)2 mortar, plaster, lime • 6.  Aluminum hydroxide Al(OH)3 deodorant, antacid • 7. Ammonia NH3 cleaners, fertilizer, rayon, nylon

11. Strong and weak bases • A strong base completely dissociates (breaks apart) in solution and releases a lot of OH-. Example: sodium hydroxide • A weak base does not completely break apart in solution and does not release as much OH-. Example: aluminum hydroxide

12. pH • There are many ways to consider acids and bases. One of these is pH. • [H+] is critical in many chemical reactions. • A quick method of denoting [H+] is via pH. • By definition pH = -log [H+], [H+] = 10-pH • The pH scale, similar to the Richter scale, describes a wide range of values • An earthquake of “6” is 10x as violent as a “5” • Thus, the pH scale condenses possible values of [H+] to a 14 point scale • Also, it’s easier to say pH = 7 vs. [H+] = 1 x 10-7

13. pH • The pH scale is a way of expressing the strength of acids and bases • Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the H+ (or OH-) ion. • pH < 7 = acid • pH > 7 = base • pH = 7 = neutral

14. pH • Indicators: substance that change color in the presence of acids and bases • Example: bromthymol blue- yellow acid/ blue base/ green neutral • phenolthalein- clear acid/ pink base/ light pink neutral • phenol red- yellow acid/ pink base/ peach neutral • methyl orange- red acid/ yellow base/ orange neutral

15. pH calculations • Kw = [H+][OH−] = 1 x 10-14 • pH + pOH = 14 • pH = - log [H+] and pOH = - log [OH-] • (The [ ] means Molarity of H+) • Example: If [H+] = 1 x 10-10 • pH = - log (1 x 10-10) •  pH = - (- 10)  •  pH = 10

16. pH calculations • 1. If [H+] = 1 X 10-5 • pH = - log (1 x 10-5) •  pH = • 2. If the molarity of H+ in a solution is x10 -4,what is the pH?

17. pH calculations • Calculating [H+] • 1. If the pH is 2 what is the [H+] • 10 -pH = [H+] • [H+] = • 2. If the pH is 7 what is the [H+]?

18. pH calculations • Calculating pOH • If [OH-] is 1 x 10 –9 • pOH = -log (1 x 10 –9) • pOH=

19. pH calculations • Calculating [OH-] • 1. If the pOH is 3, what is the [OH-]? • [OH-] = 10 –pOH • 2. If the pH is 8, what is the [OH-]? • pOH + pH = or [H+] + [OH-] = 1x10-14 • pOH= • [OH-] = 10-pOH

20. Neutralization • If you want to neutralize an acid or base, you add a buffer. • Buffers are acids, bases, or salts that are mixed with acids or bases to make their pH closer to 7. • If you want to neutralize an acid, your buffer must be a base. • If you want to neutralize a base, your buffer must be an acid. • Buffers in your body help keep your blood’s pH at 7.4. This is necessary because most of your food contains acids.

21. Neutralization • Neutralization is a chemical reaction between an acid and a base. • H+ from the acid combine with the OH- from the base to form water. • Metals from the base combine with the nonmetals from the acid to form a salt. • Example: • HCl + NaOHNaCl + H2O • Most salts are formed with a metal and a nonmetal other than oxygen. • Some salts are formed with a metal and a polyatomic ion.

22. Common Salts • Salt  formula  uses • 1. Sodium chloride NaCl food preparation • 2. Sodium bicarbonate NaHCO3 baking soda • 3. Calcium carbonate CaCO3 chalk • 4. Ammonium chloride NH4Cl batteries • 5. Sodium phosphate Na3PO4 detergents

23. Acid rain • Unpolluted rain typically has a pH value of 5.6, which is acidic, but not harmful.Any rain that is below 5.6 is considered acid rain. • Acid rain can: • 1. Dissolve marble in buildings and statues • 2. Corrode metal (buildings, cars) • 3. Kill plankton (then fish die) • Ways acid rain can occur: • 1. Burning coal releases sulfur sulfur combines with water in the air  sulfuric acid forms • 2. Car exhaust releases nitrogen oxide  combines with water  nitric acid forms • Ways to prevent acid rain: • 1. “scrubbers” in smoke stacks • 2. Nuclear power • 3. Cleaner fuel

24. Soaps, detergents, and esters • Soaps are organic salts. This means they contain carbon. • Soaps are made by reacting fats or oils with sodium hydroxide or potassium hydroxide. • Soaps made with NaOH are solids.Soaps made with KOH are liquids. Another product of this reaction is glycerin which is used in lotion. • The process of making soap is called saponification.

25. Soaps, detergents, and esters • Detergents are similar to soap, but do not form soap scum which is a precipitate that forms when soap is used in hard water (lots of minerals). This is why most laundry products are detergents , not soaps. • An ester is an organic compound formed by the reaction of an organic acid with an alcohol. Estersare responsible for the odors and flavors of flowers, fruits, and other foods. Esters are added to jello and candy to give the flavors of strawberry, banana, or apple. • Organic acids are also used to make polyester fibers.