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CHEM 3
| Question | Answer |
|---|---|
| besides the VSEPR model, what other model allows us to see 3D shapes of the molecule? | hybridization model |
| hybridization model (3) | gives additional bonding information, developed by Linus Pauling, chemical bonds are formed by overlapping of atomic orbitals |
| what are new orbitals called? | hybrid orbitals |
| how are hybrid orbitals formed? | mixing/blending of atomic orbitals |
| in what order do atomic orbitals blend? | s-->p-->d |
| what determines the type of hybridization metrics? | the geometry of the molecule |
| what two types of bonds are related to hybridization? | sigma and pi |
| which one bonds from a further distance? sigma or pi? | pi |
| sigma bonds: | formed when e- in hybrid orbitals overlap |
| pi bonds: | formed when e- in unhybridized p orbitals overlap |
| hybridization for linear shape: | sp |
| hybridization for trigonal planar shape: | sp^2 |
| hybridization for tetrahedral shape: | sp^3 |
| sp^3: (what is is, also draw it with notes) | Mixing and blending of four atomic orbitals (one s, three p) |
| sp^2: (what is is, also draw it with notes) | Mixing one s and two p (3 atomic orbitals) |
| sp: (what it is, also draw it with notes) | Mixing one s and one p (2 atomic orbitals) |
| A triple bond has _____ sigma bonds, ____ pi bonds | 1, 2 |
| A double bond has _____ sigma bonds, ____ pi bonds | 1, 1 |
| A single bond has _____ sigma bonds, ____ pi bonds | 1, 0 |
| Draw out C (lewis) as sp, sp2, and sp3. Check with chalkboard pic in notes | - |
| Draw out N (lewis) as sp, sp2, and sp3. Check with chalkboard pic in notes | - |
| intermolecular forces: | determine the macroscopic physical properties of liquids and solids (boiling point, melting point, vapor pressure) |
| intramolecular forces: | determine molecular properties (molecular shape and dipole moment) |
| 3 types of intermolecular forces: | dispersion forces, dipole-dipole forces, hydrogen bonding |
| dispersion forces (1 note and also draw out difference between instantaneous dipole and instant dipole) | all molecules have these, (check pic with notes) |
| 2 types of dipoles: | instantaneous dipole, induced dipole |
| dipole-dipole forces: (1) | only polar molecules have these (need lewis structure and VSEPR to recognize this) |
| hydrogen bonding (2): | A very strong dipole-dipole force that gets its own category Exist in molecules that have hydrogen atoms bonded to small and highly EN atoms |
| In general, the molecule that has the most IMFs will have a ______ boiling point | higher |
| IMFs stand for... | intermolecular forces |
| IMFs for nonpolar molecules: (2) | Dispersion forces increases with a larger mass and molecular shape For molecules with same mass, the one with the larger area of interaction will have a higher boiling point |
| how do we find the larger area of interaction? | use the lewis structure and shape |
| what is the order we conduct to find IMFs? | look at mass first, then area/shape |
| finding IMF for polar molecules: (3) | - Since dipole-dipole forces are found in polar substances, the more polar substance (bigger dipole moment, which we will not calculate but rather assume) will have greater IMFs - Molecules that have more hydrogen bonding tend to have greater IMFs |
| who do hybrids of N/O/F have higher bond polarity? | hydrogen bonding |
| IMFs ______ (increase/decrease) as we move closer to solid forms | increase |
| Molecules that have the most IMFs will have ______ boiling/melting points | higher |
| why do molecules that have the most IMFs have higher boiling/melting points? | because it takes more energy to break apart the IMFs |
| more viscous = ______ IMFs | higher |
| viscosity: | how thick a liquid is (thicker liquid = higher IMF) |
| surface tension: | A property of a liquid that causes their surfaces to resist external force. It happens because molecules at the surface of a liquid are attracted to each other more strongly (more IMFs) than they are to the air above them |
| which will float? a clean or a dirty paperclip? why? | clean, surface tension |
| capillary action deals with what two concepts? | adhesion and cohesion |
| adhesion: | forces between glass and water molecules |
| cohesion: | forces between the molecules |
| what liquid has a concave shape in the meniscus? why does this occur? | concave shape in meniscus (adhesion > cohesion) |
| what liquid has a convex shape in the meniscus? why does this occur? | convex shape in meniscus (cohesion > adhesion) |
| the thinner the tube, the ______ the liquid will rise | higher |
| stoichiometry: | a way for chemists to keep track of substances that are involved in a chemical reaction |
| what units does atomic mass use? | amu |
| what units does molecular mass use? | grams/molecule or amu/molecule |
| what units does molar mass use? | grams/mole |
| how does atomic mass work? (modern system- describe the conversion) | uses carbon-12 as the standard, one atom of carbon-12 is assigned a mass of exactly 12 amu |
| 1 amu = (for carbon) | 1/12 mass of one carbon atom g (1.6606 x 10^-24 g) |
| what does amu stand for? | atomic mass unit |
| how does the mass shown on the periodic table work for stoichiometry? | this mass is the weighted average of known isotopes for that element, can use this mass to calculate mass of other isotopes |
| what do you need to be able to calculate the mass of other isotopes (2) | atomic mass and % natural abundances |
| what is Avogadro's number equal to? (not the number, the unit) | one mol |
| 1/12 mass of one carbon atom (g) = | 1 amu |
| what is the mass of one Na sodium atoms (with units)? | 22.99 amu or 3.818 x 10^-23 g |
| equation to find atomic mass: | atomic mass = Σ(fraction of isotope n) x (mass of isotope n) |
| why doesn't atomic mass have a unit on the periodic table? | because it can be applied to any mol/amu |
| % mass is related to the law of... | definite proportion |
| equation to find mass % of an element: | mass % of element X = mass of element X in 1 mol of compound/mass of 1 mol of compound x 100% |
| what is the first thing needed to solve mass % equations? | molar mass (g/mol) |
| practice problem: calculate the %C and %O in CO2 | 27.3% C and 72.7% O |
| what can mass be converted to? (and vice versa) | mass --> empirical formula |
| empirical formula: | simplest whole number ratio of the atoms or molecules |
| what's the pathway from mass % to empirical formula? | mass % --> grams --> moles --> formula |
| what's the pathway from empirical formula to mass % ? | formula --> moles --> grams --> mass % |
| molecular formula: | whole-number multiple of the empirical formula? |
| which of the following is not an empirical formula? C6H8O2N2, C7H8O2N, C6H8O2N | C6H8O2N2 |
| how many orbitals on each level of sp3 hybridization? what are they called? | one level (sp3), 4 orbitals |
| how many orbitals on each level of the sp2 hybridization? what are they called? | two levels (sp2 and 2p), 3 orbitals and 1 orbital |
| how many orbitals on each level of the sp hybridization? what are they called? | two levels (sp and 2p), 2 orbitals and 2 orbitals |
| molar mass= | g/mol |
| combustion analysis: | how we determine empirical formula |
| process of combustion analysis: | 1. Burn a known mass of unknown compound 2. Weigh the amounts of products (get g of CO2 and H2O) 3. From g of CO2 and H2O, can get to moles and grams of C and H 4. Determine if O in unknown compound 5. We get the empirical formula |
| what do we need to get from grams to moles? | molar mass |
| divide by the smallest number of _____ to get empirical formula | moles |
| steps to balance an equation: | Leave the single element/molecule last to balance Start with the element only in one product Make sure same # of atoms on both sides Whole number (integer coefficients in from of each, sometimes use a fraction and will need to x both sides if so) |
| (s) = (for a chemical in a balancing equation) | solid |
| (g) = (for a chemical in a balancing equation) | gas |
| (l) = (for a chemical in a balancing equation) | liquid |
| (aq) = (for a chemical in a balancing equation) | aqueous |
| hv = (for a chemical in a balancing equation) | light |
| delta = (for a chemical in a balancing equation) | heat |
| what are all of the diatomic elements? (7) what does this mean? | H, N, O, F, Cl, Br, I, means they have N2, for example, in a chemical balancing equation |
| how to find limiting reagent? | convert given reactant amount to moles and divide by coefficient |
| theoretical yield: | the amount of product predicted by calculations from the balanced equation (based on limiting reagent) |
| actual yield: | the amount of product actually formed in a reaction |
| percent yield = | actual yield of product/theoretical yield of product x 100 |
| aqueous solution | can be dissolved in water |
| solute = | chemical component |
| solvent = | water |
| Solute + solvent | solution |
| aqueous solutions can be divided into what 2 things? | electrolyte and nonelectrolyte |
| electrolytes: (2) | can conduct electricity, separated into strong and weak |
| strong electrolytes: (3) | compounds that ionize completely: soluble ionic compounds (salts like group 1A), strong acids and bases |
| weak electrolytes: (2) | compounds that ionize partially: weak acids and bases |
| nonelectrolytes: (3) | do not conduct electricity, organic compounds (sugar, ethanol), insoluble ionic compounds |
| concentration gives us... | the amount of solute in a solution |
| molarity (M) = | moles of solute/liters of solution |
| ex: what is the molarity of table salt (NaCl, MM = 58.44g/mol) solution when you dissolve 2 tsp of NaCl in 8 oz water? (density NaCl = 2.17 g/cm^3, 1 tsp = 4.93 mL, 1 fl oz = 29.6 mL) | 1.55 M |
| two types of units for dilutions: | mg/L = ppm (parts per million) µg/L = ppb (parts per billion) |
| ex: use the equation BaCl2 -> Ba 2+ + 2Cl-, how many moles of Cl ions would be in 350 mL of a 2 M BaCl2 solution? | 0.70 moles |
| dilution eq: (also why does it only work for dilutions?) | M1V1=M2V2- only use this equation for dilutions because they’re 1:1 |
Created by:
stuisl