Chem 3

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Chem 3
2010-06-28 22:41:14

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  1. What is a solute?
    Normally the component present in the smaller amount.
  2. What is a solvent?
    The dissolving medium, normally the component present in the larger amount.
  3. What is molality?
    moles solute/ kilograms of solvent.
  4. What is molarity?
    moles solute/liters of solution
  5. What does parts per million mean? (ppm)
    A concentration of 1 ppm means that every million grams of solution contain 1 g of solute.
  6. What is the dilution equation?
    MiVi = MfVf
  7. What is electrical conductivity governed by, in the case of aqueous solution?
    It is governed by the presence and concentration of ions in solution.
  8. What are electrolytes?
    Solutes whose solutions are conductive.
  9. When is a solute considered a strong electrolyte?
    If it dissociates completely into its constituent ions.
  10. What are examples of strong electrolytes?
    NaCl and KI and molecular compounds with highly polar covalent bonds that dissociate into ions when dissolved like HCL in water.
  11. What does a weak electrolyte do in aqueous solutions?
    It ionizes or hydrolyzes incompletely in aqueous solution and only some of the solute is present in ionic form.
  12. What are examples of weak electrolytes?
    Acetic acid and other weak acids, ammonia and other weak bases and HgCl2.
  13. What are nonelectrolytes?
    Compounds that do not ionize at all in aqueous solution, retaining their molecular structure in solution.
  14. What are examples of nonelectrolytes?
    Nonpolar gases and organic compounds such as oxygen and sugar.
  15. What are colligative properties?
    The presence of solute particles can make the physical properties of a solution different from those of the pure solvent.
  16. What is vapor pressure?
    the pressure of the vapor above a fluid due to evaporated molecules.
  17. WHen does a liquid boil?
    When its vapor pressure is equal to the ambient pressure.
  18. Which is higher, the boiling point of a solution or the boiling point of a pure solvent?
    The boiling point of a solution is higher than that of the pure solvent.
  19. What happens to the freezing point of a liquid with the addition of solute?
    The freezing point of a liquid decreases with the addition of solute.
  20. What is the definition of osmotic pressure?
    The pressure that would have to be applied to a solution to prevent diffusion of pure solvent through a semipermeable membrane into that solution.
  21. What is the equation for osmotic pressure?
    pi = MRT
  22. What is reduction?
    The gain of electrons (RIG)
  23. What is oxidation?
    Loss of elections (OIL)
  24. Describe the oxidizing agent?
    It gets reduced and oxidizes something else.
  25. Describe the reducing agent.
    It gets oxidized; reduces something else.
  26. What is the oxidation number of an element in its elemental form?
  27. What is the oxidation state of a monatomic ion?
    The same as its charge.
  28. How do you assign oxidation numbers based on periodic trends?
    alkali metals (group 1): +1, alkaline earth metals (group 2): +2, etc.
  29. What are the two types of electrochemical cells?
    Galvanic cells and electrolytic cells.
  30. What is the anode and cathode?
    The anode is the site where oxidation occurs. The cathode is where reduction occurs.
  31. What is a salt bridge?
    It dissipates the presences of a charge gradient and it permits the exchange of cations and anions. They contain an inert electrolyte
  32. Describe electrolytic cells.
    Has a positive DG and is nonspontaneous. Electrical energy is required to induce the reaction.
  33. Describe Galvanic cells.
    They have a negative DG and are spontaneous and are used to do work.
  34. Where does oxidation and reduction occur?
    Oxidation at the anode; reduction at the cathode. (An Ox, Red cat)
  35. How do electrons flow (talking about electrodes)?
    Electrons flow through the wire from anode to cathode.
  36. What is the reduction potential?
    The tendency of a species to acquire electrons and be reduced. The more positive the potential, the greater the species' tendency to be reduced.
  37. What can we determine from the reduction potential of a species?
    THe species in a reaction that will be oxidized or reduced can be determined from the reduction potential of each species.
  38. What can we learn from the following:
    F2 (g) + 2e- --> 2F- (aq) Ei red = +2.87 V
    F2(g) likes to be reduced (since it has a large, positive Eired) and is therefore a strong oxidizing agent.
  39. What can we learn from the following equation:
    Li+ (aq) + e- --> Li(s) Eired = -3.05 V
    Li+ doesn't like to undergo reduction (it has a large, negative Eired).
  40. What can we learn from the following equation: Li(s) --> Li+ (aq) + e- Eiox= +3.05
    Li didn't like to undergo reduction (large, negative Eired) but flipping the equation, means flipping the signs. Therefore, Li(s) likes to undergo oxidation and is therefore, a strong reducting agent.
  41. What is used to calculate the standard electromotive force (EMF)?
    Standard reduction potentials.
  42. What is the equation for EMF?
    EMF = Eored + Eoox
  43. What are the signs of standard EMF's of a galvanic and electrolytic cell?
    The standard EMF of a galvanic cell is positive while the standard EMF of an electrolytic cell is negative.
  44. What are the three definitions of acids and bases?
    Arrhenius, Bronsted-Lowry and Lewis.
  45. Describe the Arrhenius definition of acid/base.
    An acid is a species that produces H+ (protons) in an aqueous solution, a base produces OH- in an aqueous solution.
  46. What is the Bronsted-Lowry definition of acid/base?
    An acid is a species that donates protons, while a Bronsted-Lowry base is a species that accpets protons.
  47. What is an example of a Bronsted-Lowry base but not an Arrhenius base?
    NH3 and Cl-
  48. What is the Lewis definition of an acid and base?
    An acid is an electron-pair acceptor, and a base is an electron-pair donor.
  49. Is H2O an acid or a base?
    It's both; It's either a proton donor or an acceptor toward itself (amphoteric).
  50. What is Keq for water?
    Keq= Kw= [H3O][OH-] = 1 x 10-14
  51. What is the pH?
    pH = -log[H] = log(1/[H])
  52. What pH's are considered neutral, acidic and basic?
    acidic = less than 7, basic = greater than 7 and neutral = 7.
  53. What are some examples of strong acids?
    HClO4, HNO3, H2SO4, HCl, HBr and HI.
  54. What are some examples of strong bases?
    NaOH, KOH, and other soluble hydroxides of Group IA and IIA metals
  55. What are weak acids and bases?
    They do not ionize completely and are weak electrolytes. They only partially dissociate in aqueous solution.
  56. What is a dissociation constant?
    Ka- a measure of the degree to which an acid dissociates.
  57. What is the general equation for the acid dissociation constant?
    Ka= [H3O+][A-]/ [HA]
  58. What is a titration?
    It involves the addition of a solution to determine its concentration.
  59. What occurs at the equivalence point?
    the number of moles added equals the number of moles of acid intitailly present.
  60. What is the equation for the equivalence point?
    VaMa = VbMb