Lecture contents

CH101 General Chemistry

Fall 2017

http://quantum.bu.edu/courses/ch101-fall-2017/contents.html
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Department of Chemistry | Boston University


This page lists the contents of each lecture.

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.


Lecture 1, Wednesday, September 6, 2017
Begin Mahaffy et al., chapter 2: Building blocks of materials.
Estimate the number of atoms that the lecture hall can hold. Estimate the volume occupied by the in the lecture hall after the air has been liquefied.
Lecture slides and lecture recording.

Lecture 2, Friday, September 8, 2017 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 11, 2017 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 13, 2017 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 15, 2017
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 18, 2017 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 20, 2017 Molecular ion peaks example: CH2Cl(2) molecular ion peaks are at 84:86:88 in the ratio 9:6:1. Region of electromagnetic spectrum: X-ray, UV, visible, IR, microwave, radio.
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.
Lecture slides and lecture recording.

Lecture 8, Friday, September 22, 2017 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. Wavenumber, ν̃, is the reciprocal of the wavelength in cm, 1/λ; therefore wavenumber is the number of wavelengths that can fit in 1 cm. Practice with wavelength, frequency, and wavenumber.
Lecture slides and lecture recording.