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PChem 1 Final
| Question | Answer |
|---|---|
| Mixture | Contains 2+ substances; can be homogeneous or heterogeneous |
| Homogeneous | uniform structure/composition |
| Heterogeneous | non-uniform structure; different types of particles |
| Pure substance | constant chemical composition; has distinguishing characteristics of |
| What are good differentiating characteristics? | intensive properties (melting/boiling point, density, conductivity, etc.) |
| What occurs during a phase change? | Energy is absorbed or emitted by the system |
| What does the graph of a time/Temperature graph look like? | horizontal lines at phase changes |
| What does the graph of a temperature vs. delta energy look like? | vertical lines at phase changes |
| What is phase stability? | for any substance, different phases are stable at different values of temperature and pressure |
| What is vapor pressure? | pressure exerted by a vapor when the vapor is in equilibrium with the liquid and/or solid states |
| Filtration | Based on differences in particle size |
| Distillation | based on differences in boiling points |
| What would cause a substance to have a lower or higher vapor pressure? | intermolecular forces |
| What would cause a substance to have a lower or higher melting/boiling point? | Density, IMFs, if the substance is ionic it will be higher melting/boiling points |
| What are the assumptions of the particulate model of matter? | Any macroscopic sample of a substance is composed of a large number of very small particles Particles are constantly moving in random directions through empty space Particles interact with one another. The strength of the interactions depends on the dis |
| What is true about the particles in the particulate model of matter? | They can represent anything we need them to and are static, have unrealistic proportions, and represent particles of solid objects. |
| What does temperature equal? | measure of kinetic energy per particle |
| What is pressure equal to? | the force of the particle collisions on the walls of the container |
| What is the Ideal Gas Law? | PV = nRT |
| How do we explain the existence of phase transitions? | We assume that intermolecular forces exist among particles. When temperature decreases, average kinetic energy per particle decreases, and attractive forces between particles can hold them together. |
| In the particulate model of matter, what happens as particles come closer together? What happens when they get too close together? | Particles are attracted as they come closer together, with the attraction getting stronger the closer they are, but when they are too close together, they have repulsion. |
| How can we predict the changes a system may undergo? | The PE of its components and the number of configurations its particles can adopt |
| PEC Diagrams | Show the relationship between number of possible configurations and potential energy |
| What are the ways to represent molecules? | Space-filling Ball-and-stick Molecular Formula Lewis Structure |
| Ionic compounds | Made of ions arranged in lattice networks (metal + nonmetal) |
| Lattice networks | + and - charges align into a lattice |
| formula unit | The proportions in which ions are combined in the lattice |
| AMU | atomic mass unit (1 amu = 1/2 the mass of a carbon-12 atom) |
| Avogadro's number | 6.022x10^23 particles (1 mole) |
| Molar mass | the relative mass of its particles expressed in grams |
| How do we find the mass of a liquid? | P = m/V |
| What is mass spectrometry? | 1.) particles are vaporized and broken into ions 2.) The ions are accelerated and separated by mass using a magnetic field 3.) The mass/charge ratio is recorded |
| How is a mass spectrum read? | The molecular ion peak is the tallest peak The mass of the molecular ion peak can be used to determine molecular formula |
| What is an empirical formula? | Simplest whole number ratio of elements in a compound |
| What is a molecular formula? | Number of atoms in a molecule |
| What is electromagnetic radiation? | Energy traveling through space as waves formed by oscillating electric and magnetic fields; characterized by wavelength and frequency. |
| What is absorption spectroscopy? | EM radiation is passed through an object and the radiation measured is absorbed. |
| What is an emission spectroscopy? | The measure of types of EM radiation emitted by substances when they are heated |
| What is quantization? | Electrons can only exist in certain energy states |
| What are covalent bonds? | two nonmetals are bonded by sharing atoms |
| What is the quantum model? | We cannot know both the position and velocity of an electron at the same time |
| What is electron density? | Areas in which electrons are statistically likely to be at any given time |
| What happens when bonding electrons can occupy a larger space? | Their KE and repulsive PE go down, attractive PE goes up, PE of other electrons goes down, and total energy goes down. |
| What type of radiation changes the vibrational state of molecules? | IR |
| What type of radiation can change the rotational state of molecules? | EM |
| What is atomic radius? | The distance between the nuclei of two bonded atoms |
| What is ionization energy? | The energy it takes to remove a single electron from an atom (increases as atomic radius increases) |
| What is PES? | Used to explore electron configurations |
| How is a PES graph read? | Each peak is an electron subshell |
| What is the quantum mechanical model? | There is a complex distribution of electrons within atoms. Electrons exist within clouds of probability called shells, and the subshells are called orbitals |
| What are the steps to writing the Lewis structure for a molecule? | 1.) Choose central atoms (highest bonding capacity) 2.) Count total valence electrons. 3.) Use as many electron pairs as needed to form single bonds between the central atom and surrounding atoms. 4.) Use remaining electrons to ensure all atoms have a |
| What is a sigma bond? | Head to head overlap |
| What is a pi bond? | Side-to-side overlap |
| What is a radical/free radical? | An atom that has an uneven number of electrons in a bond |
| What is hypervalency? | Elements that can break the octet rule |
| What does it mean to be electron deficient? | An atom that does not have eight electrons in a molecule |
| What is resonance? | A molecule that has more than one possible lewis structure |
| What are the rules for line structures? | 1.) Carbons are not shown; they are the "bends" and "ends". 2.) Hydrogens bonded to carbons are not shown. Their number is determined by the bonding capacity of carbon. |
| What is VSEPR? | Valence Shell Electron Repulsion Theory (regions of high electron density will be located as far away as possible) |
| Linear molecular geometry | 2 e- regions; linear e- geometry; 180 degree bond angle |
| Trigonal planar molecular geometry | 3 e- regions, trigonal planar e- geometry, 120 degree bond angle |
| Bent/angular molecular geometry | 3 e- regions, trigonal planar e- geometry, <120 degree bond angle |
| Trigonal pyramidal molecular geometry | 4 e- regions, tetrahedral e- geometry, <109 degree bond angle |
| Bent/angular molecular geometry (2nd option) | 4 e- regions, tetrahedral e- geometry, <109 degree bond angle |
| Tetrahedral molecular geometry | 4 e- regions, tetrahedral e- geometry, 109.5 degree bond angle |
| What are the steps to finding the molecular geometry of a molecule? | 1.) molecular formula 2.) Lewis structure 3.) electron pair geometry 4.) molecular geometry |
| What is electronegativity? What is the periodic trend for electronegativity? | The measure of decrease in the energy of a system if bonding electrons are localized in the vicinity of a given type of atom |
| What is a dipole moment? | the existence of partial + and - charges creates a dipole moment |
| What is a polar bond? | A bond with a dipole moment |
| What does relative IMF strength dpeend on? | polarizability > molecular polarity > bond polarity |
| What is a bond dipole? | measure of uneven distribution of valence electrons in a bond |
| What is a molecular dipole? | measure of uneven distribution of valence electrons in a molecule |
| What is polarizability? | how easily a molecule can become polar |
| What are dispersion forces? | exist in all molecules, interactions between induced dipoles |
| What causes stronger IMFs? | Larger contact area of interaction |
| What is the unit of measurement for a dipole moment? | Debye |
| What are dipole-dipole forces? | IMFs caused by permanent dipoles |
| Which IMF makes up most of the IMFs of a molecule? | dispersion |
| What is hydrogen bonding? | H bonded to N, O, or F and another N, O, or F |
| What happens when molecules have branches? | Decreases IMFs |
| What does lower IMFs cause? | Higher melting point, boiling point, and viscosity; lower volatility |
| What determines the miscibility of two substances? | The relative strength of A-A, A-B, and B-B interactions (particles will adopt states with >IMFs and <PE Relative # Configurations between M and UM states |
| What causes higher boiling point in polymers? | Polar bonds and H-bonds |
| What are polyamides? | Carboxylic Acid + Amine |
| What are polyesters? | Carboxylic Acid + Alcohol |
| What are the properties of shorter/more branches polymers? | Less rigid |
| What are additives? | substances added to polymers to adjust their properties |
| What is cross-linking? | Adding molecules to be a binder between polymer chains, increasing strength and rigidity |
| What are proteins? | Natural polymers made by the combination of amino acids |
| What are the components of an amino acid? | Amine, side chain, and carboxyl |
| What is the primary structure of a protein? | the unique sequence of amino acids |
| What are the components of a protein? | backbone with peptide bonds (carboxylic acid + amine) and side chains |
| What are unfolded polypeptides? | proteins that have just been synthesized inside a cell |
| How do proteins fold? | areas with like intermolecular forces will cause the protein to fold so that they are closer together |
| What are saturated fats? | single-bonded carbons |
| What are unsaturated fats? | at least one pair of double-bonded carbons |
| What are the two configurations each unsaturation of a fat can have? | cis (bent shape) trans (linear shape) |
| What is the general structure of triglycerides/fats? | polar head + nonpolar tail |
| What type of atoms form ionic compounds? | metal + nonmetal |
| What electronegativity difference is required for an ionic bond to form? | >2 |
| What type of ion do metals form? What type of ion do nonmetals form? | positive ions (cations) negative ions (anions) |
| How are ionic compounds containing metals with only one type of cation named? | metal + nonmetal-ide |
| How are ionic compounds containing metals with more than one type of cation named? | metal (charge in roman numerals) + nonmetal-ide |
| How are ionic compounds containing hydrates named? | Name as other compounds, but add #prefix + hydrate at the end |
| hydroxide | OH- |
| peroxide | O2(-) |
| nitrate | NO3(-) |
| nitrite | NO2(-) |
| carbonate | CO3(2-) |
| chlorate | ClO3(-) |
| chlorite | ClO2(-) |
| ammonium | NH4(+) |
| sulfate | SO4(2-) |
| sulfite | SO3(2-) |
| phosphate | PO4(3-) |
| phosphite | PO3(3-) |
| What is the nomenclature for polyatomic ions with similar sounding names? | -ate has one more O than -ite |
| What are the properties of ionic compounds? | tend to be solids, high melting/boiling points |
| What is Coulomb's Law? | F = K((q1xq2)/r^2) |
| Are cations larger or smaller than the atom they come from? | smaller |
| Are anions larger or smaller than the atom they come from? | larger |
| What causes solubility in ionic compounds? | larger ions, charges multiplied <4 |
| What is required for an ionic compound to be soluble in water? | either mixed/dissolved state has lower PE or mixed/dissolved state has > configurations |
| What are chemical processes favored by? | lower potential energy and larger number of configurations |
| What is dissolution? | The solute separates into ions or molecules - breaks attractive forces between anions and cations - promotes ion-H2O dipole interactions |
| What is assumption one of chemical reactions? | Chemical reactions are processes in which the atom that make up the reactants are rearranged |
| What is assumption two of chemical reactions? | Rearrangement of atoms during a chemical reaction produces changes in the potential energy of the particles |
| What is assumption three of chemical reactions? | For a chemical reaction to occur, particles of the different reactants must collide. (The more collisions in a given time, the faster the process) |
| What is assumption four of chemical reactions? | For a chemical reaction to occur, colliding particles must be oriented in a manner that lets reacting groups interact effectively. (< particles in the gas phase that are reactants and simpler composition and structure of particles of all reactants, faster |
| What is assumption five of chemical reactions? | For a chemical reaction to occur, colliding particles must have enough energy to reach a transition state that leads to the formation of the new products. |
| What is assumption six of chemical reactions? | As reactants interact to generate products, a reverse reaction may occur. The final state of the system is determined by the balance between these two opposite processes. |
| What is activation energy? | energy required to get to a transition state |
| What causes a reaction to be product favored? | More products once a reaction is over |
| What causes a reaction to be reactant favored? | More reactants once a reaction is over |
| What is percent yield? | (actual yield/theoretical yield)*100 |
| What is a limiting reactant? | the reactant that limits the amount of possible products |
Created by:
ltrigs
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