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CHEM 4
| Question | Answer |
|---|---|
| How can we visually tell when a precipitation reaction occurs? | the solution becomes opaque |
| Precipitation reactions: | aqueous (ionic) reactants are mixed and solid product is formed |
| Ca 2+ (aq) + CO3 2- (aq) → CaCO3 (s) is an example of a ________ reaction | precipitation |
| In the human body, precipitation reactions result in... | kidney stones |
| precipitates are _______ (soluble/insoluble) | insoluble |
| what rules are needed to predict the products in a precipitation reaction? | solubility rules |
| using the solubility rules, tell whether the following are insoluble or soluble: AgCl Ni(NO3)2 CaS BaSO4 (NH4)3PO4 | AgCl - insoluble Ni(NO3)2 - soluble CaS - insoluble BaSO4 - insoluble (NH4)3PO4 - soluble |
| how do we solve precipitate reactants into products? | using solubility rules, change the elements around to evaluate whether a precipitate will form (find soluble or insoluble), this will make the complete formula eq |
| which of the 3 precipitation formula eqs is just the full eq? | complete formula eq |
| complete ionic equation: | separate reactants on left side |
| net ionic equation: | take out spectator ions (aqueous products and therefore their reactant), what's left is net ionic |
| how do we know which are the spectator ions? | they are aqueous |
| 3 types of precipitation formula equations: | complete formula eq, complete ionic eq, net ionic eq |
| how do we know if a precipitate will be formed when mixing two reactants? | the product is insoluble |
| will a precipitate form when we mix: (NH4)3PO4 (aq) + Al2(SO4)3 (aq) | yes, the product is insoluble |
| strong acids: | hydrochloric acid (HCl), hydrobromic acid (HBr), hydroiodic acid (HI), nitric acid (HNO3), sulfuric acid (H2SO4), perchloric acid (HClO4) |
| weak acids: | formic acid (HCHO2), acetic acid (HC2H3O2), hydrofluoric acid (HF) |
| strong bases: | sodium hydroxide (NaOH), lithium hydroxide (LiOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), barium hydroxide (Ba(OH)2) |
| weak bases: | ammonia (NH3) |
| general acid base equation: | Acid (aq) + base (aq) → salt compound (aq or s) + H2O (l) |
| do the complete ionic and net ionic equation for HCl(aq) + KOH (aq) → KCl (aq) + H2O (l) | Complete ionic eq: H+ (aq) + Cl- (aq) + K+ (aq) + OH- (aq) → K+ (aq) + Cl- (aq) + H2O (l) Net ionic eq: H+ (aq) + OH- (aq) → H2O (l) |
| For this acid-base reaction, H2SO4 (aq) + Ba(OH)2 (aq), After equal moles of acid and base react and go to completion, the resulting solution will be a … (strong electrolyte, weak electrolyte, nonelectrolyte) | nonelectrolyte, because we form a precipitate |
| gases typically have a ____ molar mass | low |
| vapor: | refers to gaseous state of a substance that typically exists as a liquid |
| pressure: (definition) | Collisions of random gas particles with the walls of a container exert a force per unit area |
| pressure = (eq) | force/unit area |
| SI unit of pressure = | Pa (pascal) |
| Pa = (eq) | n/m^2 |
| what are some other types of pressure? (5) | torr, atm, bar, psi, mmHg |
| low pressure (3): | Little air above us Clouds can move in Rain/foul weather likely |
| high pressure (3): | Lots of air mass above us Clouds can't move in Sunshine/fair weather likely |
| barometer: | measures atmospheric pressure, the pressure is exerted by the mercury column, this must be the same as the exerted atmospheric air pressure (usually 760 mm) |
| manometer: | measures pressure of a gas, there are two types (closed and open) |
| what are the two types of manometers? | closed and open |
| closed-end manometer eq: | Pgas=Ph |
| what does Ph mean for a manometer? | height |
| two types of open-end manometers + their equations: | Pgas>Patm (Pgas = Patm + Ph) OR Pgas<Patm (Pgas = Patm - Ph) |
| Avogrado's law & equation: | as the amount of gas increases, volume increases, V/n=constant |
| Boyle's law & equation: | as pressure increases, volume decreases, PV=constant |
| Charles's law & equation: | as temperature increases, volume increases, V/T = constant |
| what does the ideal gas law do? | combines all 3 gas equations |
| ideal gas law eq: | PV=nRT |
| what units are all of the variables in the ideal gas law eq reported in? | P in atm V in L n in moles R in L atm/mole K T in Kelvin |
| density = mass/vol usually is in what units? | g/mL or g/L |
| how do we rewrite ideal gas law to account for molar mass/moles/grams? | PM=dRT (where M is molar mass and d is density) |
| Temp decreases, density of gas ________ | increases |
| cold air is more _____ than hot air | dense |
| STP stands for.. | standard temperature and pressure |
| STP for gases: | T = 0 degrees celsius, 273.15 K P = 1 atm |
| how to write ideal gas law to comply with STP: | V=nRT/P |
| why do larger gases tend to deviate from ideal gas laws? | they have more IMFs |
| do the practice questions in lecture 18 related to gas stoich | - |
| Gay-Lussacs Law/Law of Combining Volumes: | when you have a condition with constant P and T, you can treat volume just like moles when calculating |
| Dalton's laws of partial pressures: | the total pressure is the sum of the individual pressures |
| equation for total pressure in Dalton's law: (including moles as well, longer version) | Ptotal=P1+P2+P3+...=n1(RT/V)+n2(RT/V)+n3(RT/V)... |
| shortened Dalton's law eq: | Ptotal=ntotal(RT/V) |
| Under constant temp and volume, _____ is proportional to moles | pressure |
| what equation does Dalton's law equation leave us with? | the mole fraction |
| the mole fraction: | ni/ntotal = Pi/Ptotal (moles in individual gas/moles in total = pressure of individual gas/pressure of total) |
| do the partial pressure examples in lecture 18 | - |
| daltons law for pressure of a gas (water vapor) | Pgas=Ptotal-Ph2o |
| collisions of a gas within the walls of a container are the cause of .... | the pressure exerted by the gas |
| IMF note about Kinetic Molecular Theory: | gas particles act independent of each other, there's no attractive or repulsive forces (no IMFs) between the particles |
| the average kinetic energy of gas particles is proportional to... | the temperature (K) |
| Is the average KE higher for heavier molecules? | No, because they’re the same (only changes dependent on temperature |
| Is the speed for lighter gases faster than heavier gases? | Yes |
| where is the average speed of a gas on the graph? | at it's peak |
| Diffusion: | random mixing of gases/molecules with collisions |
| Lighter gases diffuse _______ than heavier ones | FASTER |
| Effusion: | letting gas diffuse through a pinhole |
| thermochemistry: | the study of energy changes that occur during chemical reactions |
| kinetic energy is from... | motion |
| potential energy is from... | position or composition |
| what kind of energy deals with kinetic energy? | thermal energy (associated with temperature), or translational/vibrational/rotational molecules |
| what kind of energy deals with potential energy? | chemical energy (associated with positions of electrons and nuclei) |
| transfer of heat energy always goes from ____ to ____ | hot to cold |
| 3 types of systems | open, closed, isolated |
| open system: | energy and matter freely exchanged between the system and surroundings |
| closed system: | temperature can transfer between system and surroundings (flask with lid) |
| isolated system: | temperature cannot transfer between system and surroundings (thermos) |
| what is the first law of thermodynamics? | law of conservation of energy |
| law of conservation of energy: | the energy in the universe is constant, cannot be created or destroyed, only converted from one form to another |
| initial energy of a system is the sum of... | heat energy + work |
| delta E equation: | Delta E = q + w |
| Heat (q): | energy transfer resulting from thermal differences between the system and its surroundings |
| when do energy flows stop? | at thermal equilibrium |
| Work (w): | energy transfer between a system and its surrounding, by a force moving through a distance |
| what type of molecules can do PdeltaV work? | gas molecules |
| expansion work = | -w = -PdeltaV |
| compression work = | +w = +PdeltaV |
| what does a negative sign in front of energy mean? | energy is LOST (not negative energy) |
| Endothermic reactions: | energy is gained by (or added to) the system from the surrounding (example: cold packs) |
| Endothermic reactions: deltaH = ? | + |
| Exothermic reactions: deltaH = ? | - |
| Exothermic reactions: | energy is lost (released) from the system to the surrounding (example: hot pack/combustion) |
| The total energy of a system is called _______ | enthalpy |
| _______ is the way of keeping track of the heat-related changes that happen during reactions/processes | enthalpy |
| Briefly explain enthalpy (mathematically): | total energy is defined as the sum of the internal energy and the pressure-volume product of a system |
| state function: | a property that has a unique value that depends on the present state of a system, and not on how the state was reached, nor the history of the system. Not path dependent |
| for each, tell whether they are a state function: energy: heat: work: density: temperature: | Energy: yes, a state function Heat: not a state function (path-dependent) Work: not a state function (path dependent) Heat and work are the path to energy! Density: yes, a state function Temperature: yes, a state function |
| heat capacity equation: | q=smdeltaT |
| what does each variable stand for in q=smdeltaT? (and units) | q: heat (J) s: specific heat capacity (J/g) degrees celsius m: mass (g) deltaT: temperature (celsius) |
| qrxn also equals... | n(limiting reactant) x delta H |
| another way to find deltaH: | qrxn/mol |
| heat capacity: | amount of heat needed to raise a temperature of 1g (or 1 mole) of a substance by 1 degree celsius |
| In general, a more _______ molecule/system will have a higher heat capacity | complex |
| two ways to measure deltaH (total energy of a system) | constant pressure calorimetry and constant volume calorinetry |
| device for constant pressure calorimetry | coffee cup calorimeter |
| deltaH = ? (for coffee cup calorimeter) | qp |
| equation for constant pressure calorimetry/coffee cup calorimeter | q rxn = - s m deltaT |
| deltaH = ? (for bomb calorimeter) | deltaE |
| equation for constant volume calorimetry/bomb calorimeter | q rxn = -Ccal deltaT |
| what is Ccal? | heat capacity of the calorimeter |
| Hess's law: | when the enthalpy of a reaction (deltaH) is constant, regardless of the number of steps in the process; and is the sum of the individual steps/reactions |
| equation for Hess's law | deltaH overall = deltaH1 + deltaH2 + deltaH3 |
| why do we need Hess's law? | some reactions are too dangerous/not feasible |
| rules for Hess's law: | When reversing a chemical reaction… Change the sign of deltaH for that reaction When multiplying/dividing equation coefficients Multiply or divide deltaH for that reaction accordingly |
| how do we find delta H after doing Hess's law? | figure out if we divide/multiply/reverse each equation and do that to the deltaH value (if reverse change sign) |
Created by:
stuisl