Chapter 14 : Acids and Bases

1. Chapter 14: Acids and Bases Describing Acids and Bases

2. History of theory for Acids and Bases • Arrhenius, Svante • Swedish physical chemist (1859-1927) – one of the first who attempted to scientifically describe acids and bases • Arrhenius acid • substance that, when dissolved in water, produces hydrogen ions (proton) • H+ • Arrhenius base • substance that, when dissolved in water, produces hydroxide ions • OH-

3. Examples of Arrhenius Acid and Base Arrhenius acid Arrhenius base

4. Chapter 14: Acids and Bases-- Describing Acids and Bases -- Acids- Properties • Aqueous solutions of acids are called electrolytes • Have a sour taste • Conduct electricity -- some well, some poorly • Cause some indicators, or chemical dyes, to change color • React with many metals to produce hydrogen gas • React with bases containing hydroxide ions to form salt and water • pH < 7 Bases- Properties • Conduct electricity -- some well, some poorly • Taste bitter and feel slippery • Cause some indicators, or chemical dyes, to change color • React with acids containing hydroxide ions to form salt and water • pH >7

5. Chapter 14: Acids and Bases-- Describing Acids and Bases -- Names and Formulas of Acids • Acid takes the form of HX, where H is the hydrogen ion and X is a monatomic or polyatomic ion • Rules for naming • When the name of the anion (X) ends in “–ide” - the acid name begins with hydro- - then, replace “-ide” with “ –ic”and add the word “acid” to the end. • Examples • HCl: hydrochloric acid • HBr: hydrobromicacid

6. Chapter 14: Acids and Bases-- Describing Acids and Bases -- Names and Formulas of Acids • When the anion name ends in “-ate” • the acid is named by replacing “-ate” with “–ic” and adding the word “acid” to the end. • Examples • H2SO4: sulfuric acid (since it contains the sulfate ion) • HNO3: nitric acid (since it contains the nitrate ion)

7. Chapter 14: Acids and Bases-- Describing Acids and Bases -- Names and Formulas of Acids • When the anion name ends in ”-ite” • the acid is named by replacing “-ite” with “-ous” , and adding the word “acid” to the end. • Examples: • -H2SO3: sulfurous acid (since it contains the sulfite ion) • HNO2: nitrous acid (since it contains the nitrite ion)

8. Chapter 14: Acids and Bases-- Describing Acids and Bases -- Names and Formulas of Bases • Bases are named the same way as other ionic compounds • Example: NaOH= Sodium Hydroxide • The cation is left the same • The anion is found on our list of common polyatomic ions from the back of your periodic table • ***One to know: NH3 = Ammonia • Now, let’s practice! 

9. Strengths of Acids and Bases • Acids and bases are classified into one of two categories depending on their strength • The strength depends on the amount of ions formed • The more ions formed = strong acid • Fewer ions formed = weak acid

10. Strong Bases • The strength of a base is determined by the percent of units dissociated, NOT the number of ions OH- ions produced. • This can be determined by seeing how well the substance dissociates (or separates) in solution • Example • NaOH Na+ + OH- • This is a strong base because it completely dissociates into ions when you put it in water

11. Strong Acids • Completely dissociate, or separate into ions, when mixed with water • Common strong acids and bases

12. Weak Acids and Bases • Most acids and bases are weak • Weak acids and bases only partially dissociate (or separate) when put into water • Examples • Carbonic acid is a weak acid found in soft drinks • Ammonia is a weak base found in household cleaning products

13. The pH Scale • The pH scale measures the concentration of ions in solution • Ranges from 0-14 • Neutral solutions have a pH of 7 • 0 is strongly acidic • 14 is strongly basic • The pH scale is like the Richter scale, which measures earthquakes. The change of 1 unit is a tenfold • Meaning- an earthquake with a tremor measuring 4.0 is 10x greater than one measuring 3.0.