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Lecture Summaries

CH101 General Chemistry, Fall 2018

http://quantum.bu.edu/courses/ch101-fall-2018/contents.html

This page summarizes the contents of each MWF lecture (TR lecture contents are equivalent), with links to its slides and video recording. Please note that the slides and their contents are copyrighted by Dan Dill.

Use "Find" in your Web browser to find in this page those lectures where a particular topic is discussed.

For each lecture: there is a link to the PDF of the PowerPoint slides used in that lecture and a link to the lecture recording, showing the notations made to each slide during the lecture. Click on the desired lecture number:


Lecture 1, Wednesday, September 5, 2018
Begin Mahaffy et al., chapter 2: Building blocks of materials.
Suggestions for how to approach the course. Estimate the number of atoms that the lecture hall can hold. Estimate the volume occupied by the air in the lecture hall after the air has been liquefied.
Lecture slides and lecture recording.

Lecture 2, Friday, September 7, 2018
Complete calculation of the volume occupied by the in the lecture hall after the air has been liquefied. Chemistry depends on the number of electrons in the electron cloud but not on the mass of the nucleus. Therefore, isotopes of an elements behave the same chemically. The atomic mass unit u is 1/12 the mass of one C-12 atom. Exactly 12 g of C-12 contains Avogadro's constant, NA, of atoms. Therefore, 1 u = 1 g/NA.
Lecture slides and lecture recording.

Lecture 3, Monday, September 10, 2018
How a mass spectrometer works. What a mass spectrum is. "Mass spectrum" of a chemistry class. Fractional abundances and how to use them. Average mass in terms of fractional abundances.
Lecture slides and lecture recording.

Lecture 4, Wednesday, September 12, 2018
Relative atomic mass, Ar, is the (unitless) ratio of the mass of an isotope to the mass of 1/12 of one 12C atom. Atomic weight is the (unitless) average of the relative atomic masses of the isotopes of an element. Molar mass, M, is the mass in grams numerically equal to the atomic weight, and so it is the mass in grams of NA "average atoms" of an element. Mole is NA atoms or molecules. Using mass to count numbers of atoms or molecules.
Lecture slides and lecture recording.

Lecture 5, Friday, September 14, 2018
Begin Mahaffy et al., chapter 3: Models of structure to explain properties.
Common monoatomic ions and patterns. Common polyatomic ions. Ionic compounds dissolve by formation of hydrated ions. These ions do not further come apart in water. Molecular mass spectra. The molecular ion is composed of the entire molecule. Constitutional isomers have the same empirical formula but different chemical structure. They have the same molecular ion, but otherwise different peaks in their mass spectra, since, in general, constitutional isomers fragment in different ways.
Lecture slides and lecture recording.

Lecture 6, Monday, September 17, 2018
Mass spectra can be used to identify elements in a molecule. C, O, N, H, and F each have only one important isotope. Cl has two important isotopes" 35Cl:37Cl::3:1. Br has two important isotopes" 79Br:81Br::1:1. Effect of Br and Cl on peaks in mass spectra. Light acts as oscillating tugs on charge clouds in matter.
Lecture slides and lecture recording.

Lecture 7, Wednesday, September 19, 2018
Molecular ion peaks example: CH2Cl(2) molecular ion peaks are at 84:86:88 in the ratio 9:6:1. Light acts as oscillating tugs on charge clouds in matter. Region of electromagnetic spectrum: X-ray, UV, visible, IR, microwave, radio.
Lecture slides and lecture recording.

Lecture 8, Friday, September 21, 2018
Wavelength, frequency, and wavenumber.
Lecture slides and lecture recording.

Lecture 9, Monday, September 24, 2018
Demonstration: Lighter atoms vibrate faster; atom bonded more strongly vibrate faster.
Demonstration: The more dissimilar bonded atoms are, the faster the lighter atoms vibrates.
CDF animation: Effect of relative mass and bond strength on vibration frequency.
Regions of the IR spectrum: fingerprint region, up to 1500 cm-1; double-bond region, 1500-2000 cm-1; triple bond region, 2500-2000 cm-1; and X-H region, above 2500 cm-1.
Lecture slides and lecture recording.

Lecture 10, Wednesday, September 26, 2018
Begin Mahaffy et al., chapter 4: Carbon compounds.
How the atmosphere is warmed. IR light exchanges energy with motion of atoms in molecules only if that motion shifts the centers of positive and negative charge with respect to one another. When such a shift is present the molecule is said to have a dipole moment. This means molecules such as N2 and O2 do not interact with IR light, but that molecules such as H2 do. For CO2, the symmetric stretch does not affect the charge centers and so it does not interact with IR light, but the asymmetric stretch and the bend do change the centers and so do interact with IR light.
eActivity: Collisional heating of the atmosphere, http://kcvs.ca/site/projects/JS_files/Collisional_Heating/CollisionalHeating.html.
eActivity: IR windows in the atmosphere, http://kcvs.ca/site/projects/JS_files/IR%20Window/IRWindows.html.
Report: Isotopic analysis of atmospheric CO2, https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/jgrd.50668
Lecture slides and lecture recording.

Lecture 11, Friday, September 28, 2018
Timeline of Earth's average temperature ...: http://xkcd.com/1732/
Begin Mahaffy et al., chapter 5: Chemical reactions, chemical equations.
What a chemical equation tells us. Balancing chemical equations by inspection. Stoichiometry: Amounts in chemical transformations.
Lecture slides and lecture recording.

Lecture 12, Monday, October 1, 2018
Limiting reagent. Reaction yield.
Lecture slides and lecture recording.

Lecture 13, Wednesday, October 3, 2018
Begin Mahaffy et al., chapter 6: Chemistry of water, chemistry in water.
Heat versus temperature. Heat capacity. Liquid-vapor equilibrium, vapor pressure, and boiling
Lecture slides and lecture recording.

Lecture 14, Friday, October 5, 2018
Vapor pressure and boiling.
Lecture slides and lecture recording.

Lecture 15, Wednesday, October 10, 2018
Review: Vapor pressure and boiling. Intermolecular versus intramolecular forces. Hydrogen bonding.
Lecture slides and lecture recording.

Lecture 16, Friday, October 12, 2018
Dipole-dipole interaction (polarity). Molecular polarity arises when bond dipoles do not cancel. Dipole-dipole interaction can be attractive or repulsive.
Lecture slides and lecture recording.

Lecture 17, Monday, October 15, 2018
Suggestions for how to review your exam 1 answers (lecture recording).
Induced dipole-induce dipole interaction is always attractive. Relative effect of electron cloud size (molecular weight), polarity, and hydrogen bonding on boiling points.
Lecture slides and lecture recording.

Lecture 18, Wednesday, October 17, 2018
Rationale of relative boiling points of HF, H2O, and NH3: Water can form twice as many hydrogen bonds. Predicting relative boiling points.
Lecture slides and lecture recording.

Lecture 19, Friday, October 19, 2018
Relative importance of dispersion due to lone pairs and dispersion due to bond pairs. More on how ionic solids dissolve in water. Microscopic view of aqueous ionic solution molarity: From number of water molecules to volume of water, and from number of ions to moles of ions. Solubility rules. Precipitation reactions. Concentrations after precipitation.
Lecture slides and lecture recording.

Lecture 20, Monday, October 22, 2018
Review: Concentrations after precipitation. Ionization of molecular solutes. Self-ionization (autoionization) of water. Acid-base reactions: Competition for protons, H+. Common acids and bases.
Lecture slides and lecture recording.

Lecture 21, Wednesday, October 24, 2018
Oxidation-reduction equations. Lewis acid-base reactions and complexation.
Begin Mahaffy et al., chapter 7: Chemical reactions and energy flows.
First law of thermodynamics. Signs of heat and work.
Lecture slides and lecture recording.

Lecture 22, Friday, October 26, 2018
System versus surroundings. Detecting heat, q. In chemical reactions, there is temperature change in the surroundings, but the system temperature remains constant. Predicting the sign of heat, q. If only bonds are broken q will be positive (endothermic). If only bonds made q will be negative (exothermic). If bonds are being both broken and made then the sign of q cannot be predicted with knowing relative bond strengths. Detecting work, w.
Lecture slides and lecture recording.

Lecture 23, Wednesday, October 31, 2018
Detecting work, w. The change in internal energy, ΔU = qV, is the heat flow when a chemical reaction is carried out in a sealed, rigid container so that volume is constant. The change in enthalpy, ΔH = qP, is the heat flow when a chemical reaction is carried out in a open container so that pressure is constant. Demonstrate that cooling is greater when
NaHCO3(s) + H3O+(aq) → CO2(g) + Na+(aq) + 2 H2O(l)
is carried out in an open container than when it is carried out in a sealed container: |qP| > |qV|.
Lecture slides and lecture recording.

Lecture 24, Friday, November 2, 2018
Use energy diagrams to determine the relation between qPH) and qVU) Temperature equilibration (heat leveling). Heating curves. Enthalpy change of reaction, ΔrH.
Lecture slides and lecture recording.

Lecture 25, Monday, November 5, 2018
Hess's law. Standard states and standard enthalpy change of reaction, ΔrH. Standard enthalpy change of formation, ΔfH.
Lecture slides and lecture recording.

Lecture 26, Wednesday, November 7, 2018
Using enthalpy changes of formation, ΔfH, to compute enthalpy change of reaction, ΔrH. Bond enthalpies, ΔbH. Using bond enthalpies to estimate enthalpy change of reaction. if some substances are liquids or gases, using bond enthalpies to estimate enthalpy change of reaction gives poor results .
Lecture slides and lecture recording.

Lecture 27, Friday, November 9, 2018
Begin Mahaffy et al., chapter 8: Modeling atoms and their electrons.
Review: What light is and how it interacts with matter. Natural frequencies of atoms. Light and matter exchange energy smoothly and slowly.
CDF animation: H atom 1s-2p transformation by light.
Light energy is exchanged in tiny amounts called photons. Using light-matter resonance frequencies to construct energy diagrams of matter.
Lecture slides and lecture recording.

Lecture 28, Monday, November 12, 2018
Electron waves and quantization (de Broglie): Integer number of loops (half-wavelengths); more loops,more energy.
PDF: Hydrogen atom family album.
H atom electron clouds.
Lecture slides and lecture recording.

Lecture 29, Wednesday, November 14, 2018
Energy of hydrogen atom electron clouds, En = -Ry/n2. Ry is the Rydberg, 13.6 eV. n = number of radial loops + number of nodal plane. Clouds with the same n have the same energy; we say they are degenerate. Revisit: How light and matter exchange energy.
CDF animation: H atom 1s-2p transformation by light.
The animation shows transformation of 1s to 2p by the left-right tugs of the electric field of light. The energy required in the transformation means the light wavelength is 121 nm (UV). Transformation of 1s to 2s is not possible since this would required in-out tugs of the electric field of light. We say that such s to s transformations are forbidden by the symmetry of the tugs. Transformation of 1s to 3p, 4p, etc., is possible but requires more energy from the light; more loops, more energy. The "lines" corresponding to 1s to np are called the Lyman series. The lines in the visible spectrum are due to 2s to 3p, 4p, etc., and these lines form what is called the Balmer series. (The transformation 2s to 2p is possible but because it requires zero energy change and it would not cause any energy change of the light; such a transformation is called scattering of the light.) The lines due to 3s to 4p, 5p, etc., are in the IR and form what is called the Paschen series. Summary: Light mixes together electron waves of differing numbers of differing principal quantum numbers and adds or subtracts one nodal plane.
Lecture slides and lecture recording.

Lecture 30, Friday, November 16, 2018
Review: Transformation of electron waves by light.
Light can transform an s electron cloud only to a p electron cloud.
CDF animation: H atom 1s-2p transformation by light.
Light can transform a p electron cloud into a d electron cloud.
CDF animation: H atom 2p-3d transformation by light.
Light cannot transform an s cloud into another s cloud directly. This can only be done indirectly, say as 1s to 3p, and then 3p to 2s.
Electron motion. He+ , Li2+ , etc., photon energies.
Lecture slides and lecture recording.

Lecture 31, Monday, November 26, 2018
Photoionization (photoelectric effect). Review: Lewis structures and graphical method to determine formal charge and oxidation number. More than one electron: Orbital (yikes!) approximation. Electrical shielding from the nucleus of one electron by others.
PDF: Shielding in Li 1s22s and Li 1s22p.
Lecture slides and lecture recording.