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CHEM 5
| Question | Answer |
|---|---|
| what does calorimetry find? | deltaH (total energy) |
| standard enthalpy of formation eq: | degree delta H = summation n delta Hf - summation n delta Hf |
| bond energy eq: | delta H= summation x BE (bonds broken) - summation x BE (bonds formed) |
| standard enthalpy of deltaH degree/standard enthalpy of a rxn: | The energy required when reactants in their standard states react and yield products in their standard states |
| Thermodynamic standard state: | 25 degrees C & 1 atm |
| standard enthalpy of deltaH degree f/standard enthalpy of formation of a substance | The energy involved in the formation of one moles of molecule/compound from its constituent elements, where both products and reactants are in their standard states |
| exceptions to standard enthalpies of formation at 25 degrees C | For elemental gases (H, N, Cl, O, etc), deltaHf=0 For pure element (standard state at 25 degrees C), deltaHf=0 H is an exception to ion formation |
| bond energies: | bond dissociation energy is the quantity of energy required to break one mole of covalent bonds between the atoms in a molecule (in the gas phase) |
| 2 notes about triple bonds for bond energy problems: | Triple bonds are shorter than single bonds or double bonds Takes more energy to break triple bonds |
| equation to find the energy of the interaction between the two ions: | E = (2.31e-19 J nm)(Q1Q2/r) |
| what are Q1/Q2 in E = (2.31e-19 J nm)(Q1Q2/r) | the charges of the ions |
| what is r in E = (2.31e-19 J nm)(Q1Q2/r) | the distance between the center of the ions |
| Why do ionic compounds form? | they are lower energy/more stable/more favorable |
| vapor pressure: | the pressure of vapor in equilibrium with its liquid form at constant temperature |
| when looking at vapor pressure equilibrium, what two things must be equal? | the rate of vaporization and condensation |
| Vapor pressure is _________ proportional to IMFs | inversely |
| the higher the IMFs, the _______ the vapor pressure | lower |
| how many regions on a phase diagram? what are they? | 3, solid/liquid/gas |
| what type of slope does the solid/liquid boundary have on the phase diagram | positive |
| what compound has an exception to the positive slope for fusion line rule? | water |
| triple point: | the condition in which water can exist in all 3 states |
| what is the phase change called for: solid to liquid | fusion/melting |
| what is the phase change called for: liquid to solid | freezing |
| what is the phase change called for: liquid to gas | vaporization |
| what is the phase change called for: gas to liquid | condensation |
| what is the phase change called for: solid to gas | sublimination |
| what is the phase change called for: gas to solid | deposition |
| on the heating curve, the flat slope represents _____ changes, and the upwards slope represents _____ changes | phase, temp |
| chemical equilibrium: | when the concentrations of reactants and products remain the same over time (NOT EQUAL) |
| what DOES stay equal when we reach chemical equilibrium? | the rates |
| what is K equal to for chemical equilibrium? | products ^n / reactants ^n |
| regardless of initial concentrations of reactants, when we're at equilibrium, K is the ______ | same |
| what can we turn K into when rewriting it? what do we have to do to the value? | K' or K'' --> we either have to take the reciprocal or square it |
| do the example problem on page 6 of lecture 24! | - |
| in Kp=K(RT)^delta n, what does delta n have to equal for Kp=K? | 0 |
| homogenous vs. heterogenous equilibria: | homogeneous: reactants and products in one phase heterogeneous: reactants and products in more than one phase |
| what two types of phases do we ignore when looking at Q/K | solids and liquids |
| difference between K and Q | K is calculated at equilibrium, Q is not |
| when Q is larger, which way does the reaction move? | left |
| how does the approximation rule and 5% rule work? | when K is very small, we can essentially ignore the term in the quadratic. to check our answer, whatever term we ignored (plug in x for it) should be less than 5% of the initial concentration |
| le chatelier's principle: | a system at equilibrium will respond to stress by shifting back to that point of equilibrium |
| what are the 3 things we can change for le chatelier's principle? | concentration, pressure, and temperature |
| which way will the reaction go if we increase concentration? | to the side with fewer gas molecules (and vice versa) |
| which way will the reaction go if we increase pressure? | to the side with fewer gas molecules (and vice versa) |
| which way will the reaction go if we increase temperature? (endothermic) also note: opposite is true for exothermic | q gets added as a reactant, so we shift to products side (and vice versa) |
| T/F: we can ignore multiple values for the approximation rule | TRUE |
| common ion effect: | a salt will become less soluble (shift left) if we add more of a cation/anion that is already present |
Created by:
stuisl