AnaChem Lec Finals

• What is the general equation for chemical equilibrium?

  aA + bB ⇌ cC + dD
• What happens to the concentrations of reactants and products at equilibrium?

  They no longer change.
• What does it mean that equilibrium is dynamic?

  Forward and backward reactions still occur.
• What is the equilibrium constant represented by?

  K
• What does a large K value indicate about the reaction?

  Forward reaction is favored, many products.
• What does a K value close to 1 indicate?

  Equal quantities of reactants and products.
• What does a small K value indicate about the reaction?

  Reverse reaction is favored, many reactants.
• What do we omit when writing equilibrium expressions?

  Solids and liquid water.
• What is the reaction quotient (Q)?

  Calculated like Kc using current concentrations.
• How is Q used to determine if a reaction has reached equilibrium?

  Q is compared to Kc to indicate direction.
• What is the Ksp expression for Pb(IO3)2?

  Ksp = [Pb2+][IO3-]^2
• What happens when Pb(IO3)2 is placed in deionized water?

  It dissolves until saturation is reached.
• What does the ICE method stand for?

  Initial, Change, Equilibrium.
• What is Le Chatelier’s principle?

  System shifts to oppose changes in equilibrium.
• What types of stresses can affect equilibrium?

  Concentration, pressure, and temperature changes.
• What occurs when reactants or products are added to a system at equilibrium?

  • Added reactant consumed, shift to right
  • Added product consumed, shift to left
  • No change in K
• What happens to equilibrium when pressure is increased?

  Shifts to fewer gas molecules.
• What happens to equilibrium when temperature is increased?

  Shifts to endothermic direction.
• How does the presence of Pb2+ affect the solubility of Pb(IO3)2?

  Decreases solubility due to common ion effect.
• What is the Arrhenius definition of acids?

  Substance that forms H+ ions in water.
• What is the Arrhenius definition of bases?

  Substance that forms OH- ions in water.
• What is the Brönsted-Lowry definition of acids?

  Proton (H+) donor.
• What is the Brönsted-Lowry definition of bases?

  Proton (H+) acceptor.
• What is the Lewis definition of acids?

  Electron pair acceptor.
• What is the Lewis definition of bases?

  Electron pair donor.
• What are strong electrolytes?

  Compounds that completely dissociate in water.
• What are weak electrolytes?

  Compounds that partially dissociate in water.
• What is the ionization of water?

  Water is a very weak electrolyte.
• What is the relationship between strong acids and their conjugate bases?

  Strong acids have weak conjugate bases.
• What is the relationship between weak acids and their conjugate bases?

  Weak acids have strong conjugate bases.
• What is the relationship between pKa and pKb?

  pKa + pKb = pKw.
• What is a buffer solution?

  • Resists pH changes upon acid/base addition
  • Maintains a fairly constant pH value
  • Mixture of weak acid and conjugate base or weak base and conjugate acid
• What is the Henderson-Hasselbalch equation for weak acids?

  pH = pKa + log[conjugate base]/[weak acid]
• What is the Henderson-Hasselbalch equation for weak bases?

  pOH = pKb + log[conjugate acid]/[weak base]
• What are the steps to prepare a buffer solution?

  1. Choose conjugate acid-base pair
  2. Calculate ratio of acid-base concentrations
  3. Determine buffer concentration
  4. Mix solution; adjust pH
• What is oxidation in terms of electron transfer?

  Loss of electron(s) by a species.
• What is reduction in terms of electron transfer?

  Gain of electron(s) by a species.
• What is an oxidizing agent?

  Electron acceptor; species is reduced.
• What is a reducing agent?

  Electron donor; species is oxidized.
• What is the oxidation number of free elements?

  Zero.