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Acids and Bases

Acids and Bases. Chemistry B Module 7 Textbook Chapter 20 & 21. Acids. Give up H + when dissolved in water Turn litmus red Clear in Phenolphthalein Sour taste Has pH < 7 Reacts with metal to form hydrogen (H 2 ) gas. Naming Acids (Review). Page 2 of flip book.

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Acids and Bases

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  1. Acids and Bases Chemistry B Module 7 Textbook Chapter 20 & 21

  2. Acids • Give up H+ when dissolved in water • Turn litmus red • Clear in Phenolphthalein • Sour taste • Has pH < 7 • Reacts with metal to form hydrogen (H2) gas

  3. Naming Acids (Review) Page 2 of flip book • Acids start with Hydrogen • Binary acids are Hydro___ic Acid • Ternary acids take their name from the polyatomic ion • Sulfate ion is Sulfuric Acid (H2SO4) • Nitrite ion is Nitrous Acid (HNO2)

  4. Bases • Gives up (OH)- when dissolved in water • Turns litmus blue • Pink in Phenolphthalein • Bitter taste • Feels slippery • Has pH > 7

  5. Naming Bases (Review) Page 2 of flip book • Write the name of the metal and roman numeral (if needed) • Add the hydroxide • NaOH is Sodium hydroxide • Fe(OH)2 is Iron (II) Hydroxide

  6. Arrhenius Acid-substance that produces a hydrogen ion in solution Bronsted Lowry Acid- hydrogen ion donor Lewis Acids -Accepts a pair of electrons. Arrhenius Base – a substance when in a water solution gives up an (OH)-1 Bronsted Lowry Base – hydrogen ion acceptor Lewis Bases- An electron pair donor Acid-Base Theories Page 3 of flip book

  7. Strong vs. Weak Bases Page 4 of flip book A base is strong if it contains a group I or II metal; ionizes completely • Ex. NaOH • A base is weak if it contains any other metal or (NH4)+; ionizes slightly

  8. Strong or Weak Acids? Page 4 of flip book • There are only 6 strong acids: You must learn them. The remainder of the acids therefore are considered weak acids. • HCl • H2SO4 • HNO3 • HClO4 • HBr • HI • Note: when a strong acid dissociates only one H+ ion is removed. H2S04 dissociates giving H+ and HS04- ions. • H2SO4  →   H+ + HSO41- • A 0.01 M solution of sulfuric acid would contain 0.01 M H+ and 0.01 M HSO41- (bisulfate or hydrogen sulfate ion).

  9. Common Acids and their Uses Page 5 of flip book • Hydrochloric acid (HCl) in gastric juice • Sulphuric acid (H2SO4) • Nitric acid (HNO3) • Carbonic acid in softdrink (H2CO3) • Uric acid in urine • Ascorbic acid (Vitamin C) in fruit • Citric acid in oranges and lemons • Acetic acid in vinegar • Tannic acid (in tea and wine) • Tartaric acid (in grapes)

  10. Common Bases/Uses Page 5 of flip book • Sodium hydroxide (NaOH) or caustic soda used to make soap and biodiesel, plus much more! • Calcium hydroxide ( Ca(OH)2 ) or limewater • Ammonium hydroxide (NH4OH) or ammonia water - a household cleaner • Magnesium hydroxide ( Mg(OH)2 ) or milk of magnesia – used as an antacid or a laxative • Many bleaches, soaps, toothpastes and cleaning agents

  11. Conjugate Acids and Bases Page 6 of flip book • Based on the work by Bronsted-Lowery • Examples: • HCl   +   NaOH   =>    NaCl    +   H2O    acid         base            conjugate conjugate   proton     proton            base          acid     donor     acceptor • HCl     +     NH3      =>     NH4+      +     Cl- acid            base              conjugate     conjugate                                          acid             base

  12. Sample Problems • Label the reaction with the following: Acid, base, conjugate acid, conjugate base • F-1 + H2O HF + OH-1 • NH3 + H-1 NH2-1 + H2

  13. pH Scale Page 7 of flip book • relationship between [H+] and pH • pH = -log [H+] • Definition of acidic, basic, and neutral solutions based on pH • acidic: if pH is less than 7 basic: if pH is greater than 7 neutral: if pH is equal to 7 • Explore

  14. Indicators Page 7 of flip book • Acid - Base indicators (also known as pH indicators) are substances which change color with pH. • They are usually weak acids or bases, which when dissolved in water dissociate slightly and form ions. http://www.elmhurst.edu/~chm/vchembook/180acidsbases.html

  15. Other pH indicators • Cabbage Juice • Red-acid • Blue-base • Strawberry Juice • Universal Indicator • pH 2 - pinkpH 4 - OrangepH 6 - YellowpH 8 - Aqua/BluepH 10 - BluepH 12 - Violet http://www.seed.slb.com/en/scictr/lab/food_ph/res.htm http://encarta.msn.com/media_1461500642/Universal_Indicator.html

  16. pH CalculationConvert to Molarity and put into the pH equationscientific calculators are a MUST for most of these. Page 8 of flip book • 1) 0.0015 • 2) 5.0 x 10¯9 • 3) 1.0 x 10-3 • 4) 3.27 x 10¯4 • 5) 1.00 x 10¯12 • 6) 0.00010 pH = -log[H+]

  17. pH + pOH = 14 • pOH is based on the concentration of hydroxide ion. • pOH = -log[OH-1] • pH+ pOH = 14

  18. Page 9 of flip book Neutralization • Neutralization • one type of double replacement reaction • Acid + Base Salt + water • Net ionic equation shows what drives the neutralization reaction • HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)

  19. Neutralization Problems Page 10 of flip book • HBr + Ca(OH)2 -------> • How many moles of Ca(OH)2 will it take to neutralize 15 moles of HBr? • Steps • 1. Write a balanced neutralization reaction • 2. Identify want and given • 3. Convert given to moles M x L = Moles • 4. Convert moles of given to moles of want by using coefficients. (ratio) • 5. Calculate the molarity of want = Moles/L = M

  20. Sample Problem • When 45.0 mL of 3.00 M HBr is added to 80.0 mL of Ca(OH)2 What is the molarity of the Ca(OH)2 that was neutralized?

  21. Titration Concepts Page 11 of flip book • Titration- The process which involves finding the concentration of an unknown solution by using a certain volume of a known solution. • End point- The point where neutralization is achieved and the indicator has changed color. Titration EquationMacidVacid = MbaseVbase

  22. Hydrolysis of Salts Page 12 of flip book • definition of a salt: • an ionic compound made of a cation and an anion, other than hydroxide. • the product besides water of a neutralization reaction • When you place a salt in water you get an acid and a base. • Then you have to determine if your new solution is acidic or basic

  23. Determining acidity or basicity of a salt solution • split the salt into cation and anion • add OH- to the cation • a. if you obtain a strong base. the cation is neutral • b. if you get a weak base, the cation is acidic • Add H+ to the anion • a. if you obtain a strong acid, the anion is neutral • b. if you obtain a weak acid. the anion is basic

  24. Determining acidity or basicity of a salt solution, cont. • Salt solutions are neutral if both ions are neutral • Salt solutions are acidic if one ion is neutral and the other is acidic • Salt solutions are basic is one of the ions is basic and the other is neutral. • The acidity or basicity of a salt made of one acidic ion and one basic ion cannot be determined without further information.

  25. Acidic, Basic or Neutral?

  26. Sample Problems • 1. Cu(NO3)2 • 2. KC2H3O2

  27. Sample Answer • An aqueous solution of KC2H3O2 will be basic. The K+ is the cation of a strong base (KOH), thus it is a neutral ion and has no effect on the pH of the solution. The C2H3O2- is from a weak acid (HC2H3O2), thus it is a basic ion. This compound in an aqueous solution will, therefore, form a basic solution.

  28. Sample Problem Answer • An aqueous solution of Cu(NO3)2 will be acidic. The Cu2+ is the cation of a weak base (Cu(OH)2), thus it is an acidic ion and has an effect on the pH of the solution. The NO3- is from a strong acid (HNO3), thus it is a neutral ion. This compound in an aqueous solution will, therefore, form an acidic solution.

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