Material Covered in February
Chemistry 1201
Lecture Section 3
Lecturer: Dr. Elzbieta (Elizabeth) Cook
January
March
April
May
February 27: Photoelectron effect - shows that photons of radiant energy have also particle-like properties (Fig. 6. 7)
  • Line and Band Emission Spectra (Ch. 6.3 - we will cover it quanlitatively only!)
  • The physics of the emission spectrum - atom's transitions between states (eg. between an excited state and one of the excited states) are manifested by the emission of light with appropriate wavelength (and frequency). If that wavelength falls into the 400 nm - 750 nm visible portion of the EMR spectrum, one observes colorful spectra.

    • Each atom emits a "fingerprint" emission spectrum (See Fig. 6.14 in BLB)
    Note: HOMEWORK ASSIGNMENT 2 WILL BE HANDED OUT ON FRIDAY! BE THERE!
    February 25: Chapter 6 (units 1 and 2 and a little bit of 3):
  • New terms: Ground State, Excited state(s), Electromagnetic Radiation (EMR), Wavelength (l) and frequency (n);
  • Know the relationship between l and n and be able to interconvert one into the other (eg. sample ex. 6.1)
  • Quantized Energy and Photons (Planck's Law: E photon = hn)

    • EMR has both WAVE and PARTICLE-LIKE properties (See Photoelectron effect)
    February 20: More stoichiometry - REVIEW
    February 18: ANNOUNCEMENTS:
    EXAM 1 - Friday, February 22, in-class;
    Chapters covered: 1-4
    14 multiple choice questions + 1 multipart written question
    What to bring: #2 pencils, a good eraser, calculator, scantron sheet (large)
    The following information will be provided:
  • Periodic Table of elements (containing the elemental symbol, atomic number and the average atomic mass of each element)
  • Avogadro's number
  • Solubility Table (Table 4.1 in BLB)

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    ABC of Solution Stoichiometry:

  • Analyze the question (data given, what the question is asking)
  • Balance the reaction equation (use relevant molar ratios, determine the limiting reagent if necessary)
  • Convert units (g to moles and moles to grams; molarities and volumes of solutions to moles, ...)

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    Titrations = gradual addition of a titrant to an analyte

  • New terms: analyte, titrant, buret, flask
  • calculations for a neutralization titration
  • more stoichiometry - REVIEW has started, to be continued on Wednesday!

    • February 15: Redox reactions - learn how to recognize them
    Reduction (Ox.# goes down, electrons are gained, electrons are used up)
    Oxidation (Ox.# goes up, electrons are lost, electrons are produced)
    New concepts: reducing agent, oxidizing agent
    Concentrations of solutions: MOLARITY - remember to use volume in liters! CALCULATIONS,CALCULATIONS,...
    Dilutions - remember that when dilutions are made, the number of moles of solute stays the same.
    February 8: Quiz on nomenclature.
    Oxidation numbers - RULES OF FIGURING OUT OX.#'s - know them!
    It really helps to have a good idea what the "elemental forms" of atoms are. For instance, oxygen, in its elemental form occurs as a diatomic molecule, O2 (g); copper is Cu(s), etc. Oxidation number of atoms in their elemental forms is zero (0).
    Redox Reactions: reactions where electrons "change hands" and atoms change oxidation numbers. Such reactions can rarely be balanced by inspection. - RULES OF BALANCING REDOX REACTIONS - know them!
    February 6:     Net ionic equations - continued.
    Be able to write net ionic equations for a variety of types of chemical reactions, eg. precipitation reactions, neutralization reactions, gas formation reactions, etc...
    Solubility Rules: See Table 4.1 in BLB and UNDERSTAND the kind of information it carries.
    For instance, if you are given a salt containg a chloride anion, you can see that, in Table 4.1, it says that most chlorides are actually SOLUBLE, except for chlorides of Ag+, Hg22+ and Pb2+ (this list is actully somewhat longer, but you are not responsible for knowing it all...  yet!). So, unless the salt you were given was AgCl, Hg2Cl2 or PbCl2 , the odds are that it was SOLUBLE, eg. CaCl2, NaCl, NH4 Cl, etc...
    February 4: ANNOUNCEMENT: HOMEWORK #1 has a mistake in question 5. Please, remove the coefficient of "2" from in-front of H2SiF6.
    Ch. 3.7 continued. New concepts:
  • THEORETICAL YIELD
  • ACTUAL YIELD
  • PERCENT YIELD (% yield)

    • Ch.3.5 revisited (from the lecture on Jan. 28). Combustion analysis experiment (~Fig. 3.13) was discussed.
    Recognize that CO2 collected accounts for all carbon in the sample, while all the trapped moisture (H2O) account for all the hydrogen in the sample.
    Consequently:
    nC = nCO2 (because there is ONE mole of C atoms in one mole of CO2)
                                    and
    nH = 2 nH 2O (because there are TWO moles of H atoms in one mole of H2O)
    Ch.4.1-4.2 started. New concepts: strong electrolytes , weak electrolytes and nonelectrolytes ;
    Know what happens to various substances when equeous solutions are made from them.
    Be able to classify solutions of various substances as types of electrolytes.
    Net Ionic Equations: SPLIT strong electrolytes into ions. LEAVE everything as is.
    Eg.: NaOH(aq) + HCl(aq) --> NaCl(aq) + H2O(l)
          Na +(aq) + OH -(aq) + H +(aq) + Cl -(aq) --> Na+(aq) + Cl-(aq) + H2O(l)
    cancel species which appear in the identical form on BOTH sides of the equation:

         Na+(aq)+ OH-(aq) + H+(aq) + Cl-(aq) --> Na+(aq)+ Cl-(aq) + H2O(l)

    Net ionic equation:  OH-(aq) + H+(aq)  --> H2O(l)
    Net ionic equations tell us which species truly participate in chemical reactions (here OH-(aq) and H+(aq)), and which are merely SPECTATOR IONS (here Na+ (aq) + Cl-(aq))

    February 1: HOMEWORK #1 HANDED OUT - due on February 8, 2002
    Ch.3.6-3.7: STOICHIOMETRY  !!!Lots of new concepts!!!
    Works on MOLES only (not grams, liters, etc...)
    Needs a BALANCED reaction equation.
    Balanced reaction equations carry information about MOLAR RATIOS of reactants and products.
    One can relate reactants to each other, products to each other, as well as reactants to products.

  • Coefficients in front of compounds in a balanced reaction equation define STOICHIOMETRIC EQUIVALENCES, eg. in an equation: 2 C2H6 + 7 O2 -> 4 CO2 + 6 H2O,

    • 2 moles of C2H 6 are stoichiometrically equivalent to 7 moles of O2
    as well as
    7 moles of O2 are stoichiometrically equivalent to 6 moles of H2O, etc...
  • One can produce only as much of a product as the amount of the LIMITING REAGENT, (L.R.) allows for.

    • L.R. always gets consumed first and runs out before the other reactants can completely react.
    Always determine which of the reactants is the limiting reagent, and base the amount of product(s) on the amount of the limiting reagent. (The other reactant(s) is(are) left in excess, ie. are not completely consumed)