Chapter 15

Question 1

Arrhenius acid

Answer 1

• a compound that produces H3O+ ions in aquepus solutions
• always contain covalently bonded H atoms that ionize when the compound dissolves in water
• Strong acids:
  
  • ionize completely in water(rxn goes to completion
  • Ka>>1
    
    • EX: HCl, HNO3, H2SO4 (1st dissociation only), HClO4, HBr, HI
• Weak acids:
  
  • only some molecules ionize in water

Question 2

Arrhenius base

Answer 2

• a compound that produces OH- ions in aqueous solutions
• Strong bases:
  
  • Most are hydroxides of the group 1 and 2 elements(if soluble)
  • Kb>>1
    
    • magnitude of Kb indicates base strength

Question 3

conjugat acid-base pair

Answer 3

• a Bronsted-Lowry acid and base that differ from each other only by a H+ ion: acid ⇌ conjugate base + H+
  
  • B-L acid: an H+ donor
  • B-L base: an H+ acceptor

Question 4

conjugate base

Answer 4

• the base formed when a Brønsted–Lowry acid donates a H+ ion
• Acid(aq)+H2O(l) ⇌ conjugate base(aq) +H3O+(aq)
  
  • the stronger the acid, the weaker the conjugate base and vice versa

Question 5

conjugate acid

Answer 5

• the acid formed when a Brønsted–Lowry base accepts a H1 ion
• Base(aq)+H2O(l) ⇌ conjugate acid(aq) +OH-(aq)

Question 6

leveling effect

Answer 6

• the observation that all strong acids have the same strength in water and are completely converted into solutions of H3O+ ions
  
  • strong bases are likewise leveled in water and are completely converted into solutions of OH- ions
• means that the conjugate acid of H2O (H3O+) is the strongest acid that can exist in water
  
  • also, the strongest base that can exist in water is the conjugate base of H2O: the OH- ion

Question 8

autoionization

Answer 8

• the process that produces equal and very small concentrations of H3O+ and OH- ions in pure water
• H2O(l)+H2O(l)⇌H3O+(aq)+OH-(aq)
  
  • one water molec acts as an acid and donates H+ to other that functions as a base
  • water is a pure liquid, so we don’t include its concentration in equilibrium constant expression

Question 9

pH

Answer 9

• -log[H3O+] in aq soln
• It is logarithmic, so a change in one pH unit = a 10-fold change in [H3O+]
• large pH corresponds to small [H3O+] values

Question 10

degree of ionization

Answer 10

• the ratio of the quantity of a substance that is ionized to the concentration of the substance before ionization
  
  • when expressed as a percetage…called percent ionization
  • % ionization = [H3O+]_equilibrium/[HA]_initialx100%

Question 11

monoprotic acid

Answer 11

an acid that has one ionizable hydrogen atom per molecule

Question 12

polyprotic acid

Answer 12

• an acid that has two or more ionizable hydrogen atoms per molecule such assulfuric acid(H2SO4) and phsphoric acid(H3PO4)
  
  • there are also diprotic and triprotic
• Ka1>Ka2: it is harder to remove H+ from an anion
• Usuaully only the first Ka(Ka1) effects the pH of the soln

Question 13

amphoteric

Answer 13

• can act as either an acid or base
  
  • Water!
    
    • pure water is virtually ALL molecules
      
      • it is a poor conductor

Question 14

Salts and pH

Answer 14

• Sometimes adding a salt to a soln will change the pH
  
  • conjugate bases from stron acids are so weak they won’t react with water
    
    • Br-(aq)+H2O(l)–>NR
  • group 1 and 2 hydroxides are strong bases and their cations won’t react with water
    
    • Na+(aq)+H2O(l)–>NR