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Chem 105 Midterm 3
| Term | Definition |
|---|---|
| gas properties | expandable, compressible (fills the container) no defineite shape or volume lower density mixes to form homogenous mixtures |
| kinetic molecular theory | how individual gas molecules move that explains macroscopic behavior of gases |
| KMT assumes that... 1. gases have _________ volumes compared to its container 2. move _______ and _______ 3. collide _______ with walls/other molecules 4. have no _______ interactions 5. average KE is proportional to _ (5 points) | 1. gases have insignificant volumes compare to its container 2. move randomly and constantly 3. collide elastically with walls/other molecules 4. have no intermolecular interactions 5. average KE is proportional to T |
| temperature (T) | temp is related to the avg KE of motion avergage KE - proportinal -- T |
| at any given T, all gases have the same ______ ____ | avergae KE |
| distribution of molecular speeds | at any T, gas molecules have a range of velocities (like cars on the I-15) |
| u^2rms | root mean squared speed |
| for root mean squared: T R M | T = temp in Kelvin R = gas constant (8.3145 J/mol * K) M = molar mass in kg |
| pressure | amount of force applied to an area P= F/A (force/area) |
| barometer | measures atmospheric pressure |
| how a barometer works | gravity pulls down mercury (Hg) through the column and atmospheric pressure pushes Hg into mercury pool until Fgravity =Fatm |
| manometer | measures pressure of a system |
| open systems | change in h is positive if Pgas < Patm change in h is negative if Pgas> Patm |
| closed systems | change in h of Hg is a direct measure of gas pressure |
| 1 atm is | 760 mm of Hg (=14.696 psi) |
| 1 atm=101,325 Pa 1 bar = 10^5 Pa | so 1 atm is about = 1 bar |
| as temperature increases, distribution gets wider and | avergae speed gets higher |
| speed is proportional to | temp |
| speed is inversely proportional to | mass |
| larger molcules move smaller molecules move | slower faster |
| effusion | gas escaping from a container through a tiny hole into a region of lower concentration ex: party balloon diffusing |
| diffusion | spread of one gas through another gas ex: smell of pot-roast when coming home from church |
| for both effusion and diffusion | heavier gases efuse/difuse slower light gases efuse/difuse faster |
| Graham's law | rate (mole/sec) of effusion/diffusion is inversely proportional to density inversely proportional to M^1/2 |
| KMT - ______ view | microscopic |
| gas laws - ______ view | macroscopic observation of gases, relating properties we can easily measure |
| P | pressure atm, Pa, mm Hg |
| V | volume of the gas L, m^3 |
| T | temperature in Kelvin (sometimes in special cases in Celsius) |
| n | amount/# of moles |
| why hot air balloons float? | lower gas density inside the balloon than outside the balloon can come from lower molar mass or higher T (so bigger V) |
| warm/moist air is ___ dense than cold, dry air | less dense, which rises to the top, the cold, more dense air sinks. at the higher altitude, the temp is colder, causing the water to condense, from clouds, and then form rain |
| Boyle's law | PV = constant |
| volume ______ as pressure _________ | volume decreases as pressure increases |
| Amonton's Law | P/T = constant |
| P ________ as T ________ | P increases as T increases |
| Charles's Law | V/T = constant |
| V ______ as T ________ | V decreases as T decreases |
| Avogadro's law | V/n = constant |
| V ________ as n ________ | V increases as n increases (directly proportional) |
| combined gas law | PV=nRT R is gas constant |
| STP | standard pressure and temperature 1 atm, 273.15 K 1 mol of any gas at 0 C and 1 atm --> V of 22.4 L |
| (density) d= | PM/RT |
| (molar mass) M= | mRT/PV |
| in resonance structures the bond order is delocalized across all molecules meaning that | the bond order is the same for all bonds |
| larger atoms - shorter atoms - | longer, weaker bonds stronger, smaller bonds |
| 1 or more stereo centers means that | the molecule is chiral |
| 1 or more stereocenters means that | an enantiomer of the molecule is possible |
| anti-bonding nodes are always ___% between two nuclei | 50 perfect half and half |
| metals are good conductors because metals have a _____ amount of delocalized electrons that can move easily across the metal electrons can easily move across a metal because the HOMO and LUMO bands ______ | metals are good conductors because metals have a LARGE amount of delocalized electrons that can move easily across the metal electrons can easily move across a metal because the HOMO and LUMO bands OVERLAP |
| air is a mixture of | gas |
| air is made up of | 78% N2 20.9% O2 09% Ar 0.17% other gases 0.03% CO2 |
| diatomic gases | Br I N K Cl H O F |
| total pressure = | sum of all partial pressures |
| mole fraction | ratio between moles of one component and the total moles present X1 = n1/ntotal |
| mole fraction and partial pressure equation MUST HAVE MEMORIZED | P1 =( X1)(Ptotal) |
| collecting gas over water | volume of gas collected adjusts so that total pressure = atmospheric pressure |
| to get gas when it was collected over water | subtract partial pressure of water from total pressure |
| deviation due to repulsion between molecules, PV is ______ than "ideal" | deviation due to repulsion between molecules, PV is BIGGER than "ideal" |
| deviation due to attraction between molecules, PV is ______ than "ideal" | deviation due to attraction between molecules, PV is SMALLER than "ideal" |
| when calculating root mean squared, put molar mass in ___ which means R should be in __ (kg*m^2) | molar mass - kg R - J/mol*K |
| INTRAmolecular forces vs INTERmolecular forces | INTRA - between a molecule (covalent, metallic and ionic bonds) INTER - between 2 seperate molecules |
| which is strong intramolecular forces or intermolecular forces? | intramolecular forces |
| london dispersion forces | tiny momentary shift in electron density temporary dipole weakest bonds |
| polarizability | relative ease with which the electron cloud can be distorted |
| london dispersion forces are _____ present, and in nonpolar molecules they are the ____ option | ALWAYS present, ONLY option for nonpolar |
| london dispersion strength = ___ KJ/mol | 1 |
| larger molecules are more polarizable than smaller ones because they have a | larger electron cloud to disort |
| intramolecular forces have smaller atoms with short, smaller bonds but intermolecular forces (dispersion) have ______ forces with larger atoms instead | larger |
| more surface area = more polarizable = | greater london dispersion forces ex: linear molecules have greater polarizability (meaning their london forces are stronger) |
| dipole-induced dipole | interaction between polar and nonpolar molecule |
| dipole-induced dipole strength = | 1-5 KJ/mol |
| dipole-dipole | interaction between polar molecules +/- ends attract |
| dipole-dipole strength = | 5-20 KJ/mol |
| H-bonding | strongest dipole-dipole interaction occurs between H with NOF tug of war with H in between |
| H-bonding strength | 30-150 KJ/mol |
| ion-dipole | interactions between ions and polar molecules ex: NaCl dissolves in H2O, pulls anions/cations away |
| ion-dipole strength = | 150+ KJ/mol |
| ion-ion | strongest, about same energy as covalent bonds leads to solids with high melting temps |
| H bonding donor and acceptor | donors - H atoms covalently bonded to NOF, makes H positive acceptors - NOF that has a lone pair |
| density of H2O | decreases as water freezes, ice is less dense than water so it floats liquid H2O - mess of H bonds solid - hexagonal crystal lattice that takes up more space |
| solute | smaller amount of moles, substance being dissolved |
| solvent | part doing the dissolving, often has greater amount of moles |
| solvation (sphere of hydration) | the solvent pulls solute particles apart and surrounds, or solvates them |
| solubility | max quantity of a substance that can dissolve in a given volume of solution |
| miscible | mutually soluble in any proportion 2 liquids mix to form uniform solution (salt in water) |
| immiscible | not soluble in any proportion do not mix, forms layers (oil and water) |
| water is the | universal (polar) solvent - dissolves more substances than any other liquid |
| adhesive forces | between unlike particles meniscus: concave (a valley) |
| cohesive forces | between like particles meniscus: convex (a hill) |
| capillary action | when a liquid spontaneously flows up a narrow tube against the force of gravity (in trees) (cohesion + adhesion) |
| viscosity | measures resistance to flow stronger IM forces = higher viscosity (molecules stick together well) honey, molasses |
| volatility | tendency of substance to vaporize (escape into gas phase) weaker IM = higher volatility (higher vapor pressure) |
| vapor pressure | pressure exerted by the vapor over the liquid in a closed container when in dynamic equilibrium weaker IM forces = higher vapor pressure |
| Under which set of conditions (both pressure and temperature) are gases most likely to deviate from ideality? | high pressures and low temperatures At high P, gas molecules are forced together, so IM forces and the volume of particles become significant At low Temp, gas molecules move more slowly, so attractive forces between them have a greater effect |
| constant a | corrects for intermolecular attractions between gas molecules a = ___ L^2 atm mol^-2 |
| constant b | corrects for finite volume of gas molecules themselves b= ___ L mol^-1 |
| a molecule has to be ____ in order to form H bonds | polar |
| physical states of matter (solid, liquid, gas) | a competition between IM and KE when KE (temp) exceeds the energy of the IM forces at a certain P, the substance changes states |
| phase diagram | graphical representation of a substance's physical state changes with T and P |
| lines on a phase diagram | equilibrium between 2 physical states, seperate each phase |
| triple point | equilibrium between all 3 phases |
| critical point | above this point there is no difference between gas/liquid, is a supercritical fluid |
| supercritical fluid | halfway between gas and liquid - effuse through solids like a gas - can dissolve materials like liquid |
| boiling occurs when vapor pressure = | atmospheric pressure |
| normal boiling and melting point are at | 1 atm |
| boiling point is lower at _____ altitude | high |
| at high altitude, water boils at a ______T, takes ____ to cook food | lower, longer |
| lower boiling point = _____ IM = _____ vapor pressure | weaker IM, higher vapor pressure |
| solid/liquid line is usually a _____ slope | positive slope which means solid is more dense than liquid |
| exception: water has a _____ solid/liquid slope | negative ice is less dense than liquid water |
| gas that behaves the most ideally | H2 |
| hydrocarbons: the heavier and more linear they get, the more _______their electron cloud is, and the more _______their London-dispersion forces are. | heavier = more polarizable = more powerful/strong london dispersion forces |
| the ability to form a solution depends on the tendency of substances to ______ and ______, not to remain in small, isolated volumes. | disperse/mix |
| solutions form when solute - solvent forces are stronger than | solvent-solvent and solute-solute forces |
| solution is also called | homogenous mixture |
| noble gases (like Ar) are | nonpolar, hydrophobic, does not form with water |
| N2 is | nonpolar |
| the longer the hydrocarbon chain, the more _____ it is, meaning it is ____ soluble in a nonpolar solvent | the longer the hydrocarbon chain, the more NONPOLAR it is, meaning it is MORE soluble in a nonpolar solvent |
| the longer/more linear the hydrocarbon chain, the stronger the forces and the ____ volatile it is | less |
| KMT assumes that... (5 points) | 1. gases have insignificant volumes compare to its container 2. move randomly and constantly 3. collide elastically with walls/other molecules 4. have no intermolecular interactions 5. average KE is proportional to T |
| M vs m | M - molar mass m - mass |
| stoichiometric coefficients | ratios of reactants and products ratios of moles |
| combustion reaction | CxHxOx + O2 --> CO2 + H2O |
| complete combustion | all C goes into CO2 |
| incomplete combustion | some CO or soot produced |
| electricity | coal pulverized (crushed into power) --> combusted --> heat --> boils water --> steam --> rise to turn turbines --> electricity |
| remember that atoms and line pairs will arrange themselves in equatorial positions around the central atom, making them all evenly spaced and thus the whole molecule is | symmetrical and nonpolar |
| SN=2 linear | nonpolar (if both atoms on the ends are the same) ex: BeCl2 (polar if atoms on the end are different - asymmetrical) |
| SN=3 trigonal planar | nonpolar ex: BF3 |
| SN=3 bent | polar ex: SO2 |
| SN=4 tetrahedral | nonpolar ex: CH4 |
| SN=4 trigonal pyramidal | polar ex:NH3 |
| SN=4 bent | polar (not symmetrical, because angles are pushed down) ex: H2O |
| SN=5 trigonal bipyramidal | nonpolar ex: PCl5 |
| SN=5 seesaw | polar ex: SF4 |
| SN=5 T-shaped | polar ex: ClF3 |
| SN=5 linear | nonpolar (all three lone pairs are on equatorial positions) ex: XeF2 |
| SN=6 octahedral | nonpolar ex:SF6 |
| SN=6 square pyramidal | polar ex:BrF5 |
| SN=6 square planar | nonpolar ex: XeF4 |
| SN=6 T-shaped | polar ex: very rare |
| SN=6 linear | nonpolar ex: very rare |
| the full positive or negative charge on an ion makes it the _____ interaction | strongest |
| CCl2F2 is polar because... | its tetrahedral, and the angles are 109.5, meaning that the angles can't cancel out --> think of the SHAPE |
| if a structure is has any charge at all on it, it can form __________ interactions with water | ion-dipole |
| polarizability | how easy/hard it is to distort electons anaologies: how easy it is to pull/move around a soft squishy "atom" how hard it is to shove 5 strong, stood together athletes (low polarizability) vs how easy it is to shove around many children (high pol. ) |
| what makes more polarizability? ______ atomic radius ______ electrons ______ spread out/elongated (surface area) | larger atomic radius more electrons more spread out (more surface area) |
| empirical formula | experimental lowest whole number ratio of elements |
| molecular formula | always a whole number multiple of the empirical formula |
| Why big nonpolar molecules dissolve better in nonpolar solvents | LDForces get stronger as molecules get bigger and have more electrons. Methane (CH₄): tiny - weak LDforces Decane (C₁₀H₂₂): large - strong LDforces Decane’s strong dispersion forces match the solvent’s forces → better dissolving |
| Solubility isn't about being _____. It's about being ______ | Solubility isn't about being small. It's about being similar |
| however, in polar solutions, a larger hydrocarbon chain is harder to dissolve, because the bigger it is the more _______ it becomes | nonpolar, which is unlike the polar solution |
| Na+(aq) | dissolved in aqueous solution means dissolved in water so this forms an ion-dipole IM force --> very strong |
| HCl (dipole-dipole) KBr (ion-ion) | this is a covalent molecule, these are not ions unless they are dissolved in water and broken up KBr is an ionic compound and is solid |
| O2 bonded to water is _______ because in order for it to be H-bonding you need a ______ on oxygen | dipole-induced dipole, donor H |
Created by:
anyasalmon