Midterm Exam 3

See below for a comprehensive summary of the topics included on the exam. While the end of chapter problems in the textbook are always a great place to start, the REVIEW MATERIALS page has many additional practice problems and their answer keys. Use the iClicker Questions to review common misconceptions & typical mistakes. Remember, the annotated lecture slides are also posted to the course schedule.  If you need additional review, you can always consult the video tutorials and animations posted for each lecture (also found on the course schedule).

Midterm Exam 3 Topics:

All relevant equations will be provided; there is no need to memorize equations or unit conversions.

• Electromagnetic Waves:
• Frequency, wavelength & their relationship
• Amplitude
• Nodes

• Electron Orbitals:
• Shape of s, p, & d orbitals
• Know how to write the electron configurations up to Calcium
• Be able to identify which electrons are CORE electrons & which are VALENCE electrons
• Understand how Group Number in the periodic table relates to VALENCE ELECTRONS
• Be able to use these steps to write VALID Lewis Dot Structures Download use these steps to write VALID Lewis Dot Structures
• Understand how electronegativity varies throughout the periodic table
• Understand the OCTET Rule and when it is violated
• VSEPR Theory:
• Understand the basic premise behind VSEPR Theory:
• Electron regions repel one another and generate electron geometries with the maximum space between these regions
• Be able to count the number of bonding regions, and lone pairs coming off a central atom to find the total number of electron regions
• Use the number of bonding regions to determine the electron geometry
• Know the difference between electron geometry and molecular geometry, and determine the molecular geometry once the electron geometry is known:
• Know the bond angles for each type of shape
• Be able to draw sketches of the molecules depicting their three-dimensional arrangement
• Polarity:
• Know the cut-offs below for distinguishing between nonpolar covalent, polar covalent and ionic bonds. Understand how differences in electronegativities relate to the types of bonds below.
• Nonpolar Covalent: $\Delta EN\le0.4$
• Polar Covalent:$0.4<\Delta EN\le2.0$
• Ionic:$\Delta EN\:>2.0$
• Be able to classify bonds according to the categories above
• Be able to draw dipole moment vectors and partial charges to describe charge separation in polar covalent bonds
• Use Lewis dot structure, bond polarities and molecular geometry to classify the molecule as POLAR or NONPOLAR Download Use Lewis dot structure, bond polarities and molecular geometry to classify the molecule as POLAR or NONPOLAR
• Understand how the symmetry of a molecule can cause dipole moments to cancel (resulting in a NONPOLAR molecule) or add together (resulting in a POLAR molecule overall)
• Gas Laws: Understand the basic behavior of gases and how one variable like pressure is affect by other variables like volume, temperature or number of moles of gas. Use the gas laws below to quantify these relationships:
• Boyle's Law: $P_1V_1=P_2V_2$ assuming constant temperature (T) and fixed quantity of gas (n)

• Charles' Law: $\frac{V_1}{T_1}=\frac{V_2}{T_2}$  assuming constant pressure (P) and fixed quantity of gas (n)

• Gay-Lussac Law:  Links to an external site.$\frac{P_1}{T_1}=\frac{P_2}{T_2}$  assuming constant volume (V) and fixed quantity of gas (n)

• Combined Gas Law: Links to an external site. $\frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2}$   assuming a fixed quantity of gas (n)
• Avogadro's Law: Links to an external site. The number of moles of a gas and its volume are directly proportional [assuming constant temperature (T), constant pressure (P) and constant volume (V)]
• TIP: All of the gas laws above can be derived from the Ideal Gas Law (PV=nRT). Be Lazy! Don't memorize the gas laws! Links to an external site.
• Ideal Gas Law: PV=nRT Links to an external site.
• Practice Problems Links to an external site.
• Always use temperature in KELVIN: $Kelvin\:=\:^oC\:+\:273.15$
• Be sure all units are consistent with one another. For example, if pressure is reported in psi (pounds per square inch), mmHg and kilopascals (kPa), it's probably best to get everything into a standard unit like atmospheres (atm) using the unit conversions provided
• Use the right form of R (the Universal Gas Constant) so that the units are consistent throughout the problem:
• R = 0.08206 Latm/molK
• R = 62.37 LmmHg/molK
• R = 8.314 LkPa/molK
• Use the ideal gas equation to find the number of moles of a gas given pressure, temperature and volume of a gas, or vice versa: find the volume of a gas given the number of moles of the gas + temperature and pressure.
• Know how to solve for the density of a gas given its temperature and pressure. Links to an external site.
• Know how to solve for the molar mass of a gas given its density, temperature and pressure. Links to an external site.
• Use Avogadro's law and stoichiometric analysis to determine the volumes of gases needed for complete stoichiometric reactions. Links to an external site.