Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
EK Chem 3
thermo
| Question | Answer |
|---|---|
| extensive properties | properties that are proportional to the size of the system |
| intensive properties | properties that are independent of the system |
| state function | pathway independent, the state property going from 1 state to another is the same regardless how system was changed |
| heat | movement of energy via conduction, convection, or radiation - always from hot to cold |
| convection | thermal energy transfer via fluid movements |
| radiation | thermal energy transfer via electromagnetic waves, related t T^4 |
| conduction | thermal energy transfer via molecular collisions - requires contact |
| PV work | W = P*deltaV (constant pressure)` |
| 1st law of thermodynamics | energy of the system and surroundings is always conserved, any energy change must equal heat flow into system plus the work delta(E) = q + w (work on the system is positive) |
| 2nd law of thermodynamics | heat cannot be changed completely into work in a cyclical process entropy of isolated system will never decrease |
| carnot efficiency | e = 1 - Tc/Th |
| internal energy | collectve energy of molecules measured on a microscopic scale, often referred to as heat, thermal energy, state function |
| zeroth law of thermodynamics | two bodies in thermal equilibrium share a thermodynamic property - which is a state function -- TEMPERATURE EXISTS |
| KEavg = | =3/2*kT where k is Boltzman constant |
| enthalpy | manmade property that accounts for extra capacity to to PV work, defined as H = U + PV, not conserved like energy, not constant (of the universe), state function |
| change in enthalpy at constant pressure | delta(H) = delta(U) + P*delta(V) |
| standard enthalpy of formation | change in enthalpy for rxn that creates 1 mole of a cmpd from raw elements in their standard state |
| if gas is not part of the rxn, the enthalpy change is... | equal to the heat, which in the absense of work is equal to a change in energy |
| heat of rxn | delta(Hrxn) = delta(Hf of products) - delta(Hf of reactants) |
| Hess' law | when you add rxns, you can add their enthalpies; also, forward rxn = neg of reverse rxn |
| exothermic rxns have a positive or negative enthalpy | negative |
| endothermic have a positive or negative enthalpy | postive |
| if gas is not part of the rxn, the enthalpy change is... | equal to the heat, which in the absense of work is equal to a change in energy |
| heat of rxn | delta(Hrxn) = delta(Hf of products) - delta(Hf of reactants) |
| Hess' law | when you add rxns, you can add their enthalpies; also, forward rxn = neg of reverse rxn |
| exothermic rxns have a positive or negative enthalpy | negative |
| endothermic have a positive or negative enthalpy | postive |
| if gas is not part of the rxn, the enthalpy change is... | equal to the heat, which in the absense of work is equal to a change in energy |
| heat of rxn | delta(Hrxn) = delta(Hf of products) - delta(Hf of reactants) |
| Hess' law | when you add rxns, you can add their enthalpies; also, forward rxn = neg of reverse rxn |
| exothermic rxns have a positive or negative enthalpy | negative |
| endothermic have a positive or negative enthalpy | postive |
| if gas is not part of the rxn, the enthalpy change is... | equal to the heat, which in the absense of work is equal to a change in energy |
| heat of rxn | delta(Hrxn) = delta(Hf of products) - delta(Hf of reactants) |
| Hess' law | when you add rxns, you can add their enthalpies; also, forward rxn = neg of reverse rxn |
| exothermic rxns have a positive or negative enthalpy | negative |
| endothermic rxns have a positive or negative enthalpy | positive |
| entropy | nature's tendency to create the most probable situation that can occur w/in a situation, state f(x), extensivy property (increases w/ amt of substance) |
| delta(Suniverse) | >=0 = delta(Ssystem) + delta(Ssurroundings) |
| entropy of system can decrease only if | at the same time, the entropy of the surroundings increase by a greater or equal magnitude |
| ideal reactions create how much entropy change? | zero - meaning they are reversible |
| if a rxn is unfavorable in terms of enthalpy, but increases entropy, will the rxn occur? | yes, entropy is the driving force that dictates whether or not it will proceed |
| 3rd law of thermodynamics | assigns by convention a zero entropy value to any pure substance at absolute zero and in internal equilibrium |
| units of entropy? | J/K |
| change in entropy related to heat eqn | delta(S) = dqrev/T where dqrev is the infinitesimal change in heat per kelvin |
| Gibb's free energy | delta(G) = delta(H) - T*delta(S) (all of the system not surroundings), extensive property, state function, represents maximum non-PV work available from rxn |
| when delta(G) is negative… | the rxn is spontaneous |
| with +delta(H) and -delta(S), delta(G) will be.. | positive |
| with -delta(H) and +delta(S), delta(G) will be… | negative |
| what is value of gibb's free energy at equilibrium? | zero |
| when both enthalpy and entropy are the same sign, free energy will be.. | positive or negative, therefore spontaneity of rxn will depend on the temperature |
Created by:
miniangel918
Popular MCAT sets