Ch. 6 Flashcards
what is thermodynamics
the transformation of energy from one form to another
what is the zeroth law of TD
if 2 systems are both in thermal equilibrium with a third system, the the 2 initial systems are in thermal equilibrium with one another. (DEFINES TEMP)
what is the first law of TD
the total energy of the universe is constant.
what is enthalpy
the measure of the heat energy that is released or absorbed when bonds are broken and formed during a reaction
bond forming causes energy to
releases energy enthalpy is negative
bond breaking causes energy to
consumed energy enthalpy is positive
reactants having more energy than products means the reaction is
exothermic where enthalpy is (-), making products more stable/less energy
products having more energy than reactants means the reaction is
endothermic where enthalpy is (+), making reactants less stable/more energy
what is standard conditions
when temp is 25 C or 298 K and pressure is 1 ATM and conc=1M
what is heat formation
the amount of heat energy required to make one mole of a compound from its natural elements in natural state. O2 is common to be seen therefore has 0 Hf where O3 isnt normally found in nature and has Hf of 249 kj/mol
what does hess law state
if a rxn occurs in several steps, then the sum of the energies absorbed or given off in all the steps will be the same as that for the overall rxn.
what are the rules when using hess’s law
- if rxn is reversed, most thermodynamic quantities are reversed in sign
- if equation is multiplied by a coefficient, then TD quantities must be multiplied by the same value
what is entropy
measurement of disorder/randomness
what is the 2nd law of TD
the disorder of the universe is increasing in a spontaneous process
what is 3rd law of TD
the least thermally energetic state and lowest achievable temp at 0 kelvin where entropy is zero and temp is 0
what is gibbs free energy
the change in delta g is the energy that is available to do useful work in a rxn
entropy depends on temp therefore at low temp, what occurs? high temp?
low temp: enthalpy is the dominant factor
high temp: entropy is dominant
if H=+ and S=+ what is delta g in low and high temps
low: (+)= G non spon
high: (-)=G spon
if H=- and S=- what is delta g in low and high temps
low: (-) spon
high: (+) nonspon
in terms of spon, high reactants and low products is what type of rxn
spon exergonic (unstable to stable) we always want to go to lower energy states there for more rxns that are favorable are spon
in terms of spon, low reactants and high products is what type of rxn
non spon endergonic (stable to unstable)
what does kinetics deal with
how fast the reaction will occur
what is important to note about diatomic elements in relation to enthalpy
diatomic elements (F2, Cl2, O2) that are in there natural state (gas usually but check), have zero enthalpy
what is formula to find enthalpy of a reaction?
H of products- H of reactants
what is formula to find enthalpy of bonds being broken in a reaction?
H of bonds breaking (reactants) - H of bonds being formed (products)
what has more entropy one mol or three mols?
more mols calls for more entropy
an isoelectronic species have the same what
electron configuration
a negative value of enthalpy indicates
weak electrostatic forces and effective solvation by water
what is a isoelectronic species
something with the same number electrons
