AP Chemistry Unit 3 - Intermolecular Forces and Properties

University:
Kentucky State University
Course:
CHE 101 | General Chemistry I
Academic year:

2022
Views:

378

Pages:

5
Author:

Malcolm Li

Unit 3 - Intermolecular Forces and Properties Nonpolar molecule - bond dipoles cancel out due to symmetry General ranking of IMF strength from weakest to strongest: LDF, dipole-dipole, hydrogenbonding, ion-dipole, ionic bonding (look at chart) ● London dispersion forces (or Van der Waals forces) occur when the instantaneous dipole (caused by moving electrons in an individual atom) in one atom can cause another atom to have an uneven distribution in its electron cloud. ● The attractions between POLAR molecules are called dipole-dipole interactions. This is when the partial positive end is attracted to the partial negative end of another molecule. ● Hydrogen Bonding is a strong dipole-dipole interaction that occurs between a Hydrogen atom and either F, O, or N (H-F, H-O, and H-N) ● Ion-dipole forces are INTERPARTICLE. This is the attractive force between an ion and a polar molecule. Temperature is a measure of average kinetic energy. Covalent network solids - strong covalent bonds in a 3D network often with carbon and/or silicon i.e. diamond, SiO2 Use ratio reasoning to determine relationship between gas law variables - if two variables are on the same side of the equation, raising one will decrease the other, if they are on opposite sides, raising one will raise the other KMT - Gas molecules move in straight lines unless they collide(causing pressure), average kinetic energy = temperature, gas molecules have no volume and exert no attractive/repulsive forces(do not lose energy during collisions) ● Deviations: gases do have volume and exert attractive/repulsive forces at high pressure, low temperature, and low volume Phase Diagram is a convenient way of representing phases of substance as a function of temperature and pressure. Triple Point is when all the lines are met. Critical Point is when gas can’t be made to liquefy no matter how great the pressure and te Combined Gas Law: If we combine all these laws, we get the Ideal Gas Law: PV=nRT **R= gas constant=0.08206 atm mol-1 K-1 STP is standard pressure at 1 atm and standard temperature of 273 K. Also, under STP, 1 mol equals to 22.4 L. Dalton’s Law of Partial Pressures: In a homogeneous mixture the macroscopic properties do not vary throughout the sample. In a heterogeneous mixture, the macroscopic properties really depend on that specific location in the mixture. Substances with similar intermolecular interactions tend to be soluble with one another. Same with polar and nonpolar substances. “Like dissolve like” Root Mean Square Velocity M is the molar mass of gas in kg/mol. R=8.3145J/K*mol. Final Unit is in m/s Diffusion: the mixing of gas Effusion: The passage of a gas through a tiny orifice into an evacuated chamber. Graham’s Law of Effusion: R represents the rate of effusion for each gasses. 𝑅𝑒𝑡𝑒𝑛𝑡𝑖𝑜𝑛 𝑓𝑎𝑐𝑡𝑜𝑟 𝑜𝑓 𝑐ℎ𝑟𝑜𝑚𝑎𝑡𝑜𝑔𝑟𝑎𝑝ℎ𝑦 𝑅 𝑓 = 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑒𝑑 𝑏𝑦 𝑠𝑎𝑚𝑝𝑙𝑒 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑒𝑑 𝑏𝑦 𝑡ℎ𝑒 𝑠𝑜𝑙𝑣𝑒𝑛𝑡 Beer’s law for colored solutions - A=abc, absorption of light by a solution=(a constant unique to given molecule)(path length)(concentration of solution) ● Absorbance is proportional to concentration of a solution ● To predict possible experimental error, decide how the error affects the equation and use ratio reasoning, i.e. if water is left in a cuvette, concentration of the solution would be less, so absorbance would be less