kinetics and equilibrium Flashcards
kinetics
branch of chemistry concerned with eh rate of chemical reactions and the mechanics by which they occur
elementary reactions
the series of steps that form a chemical reaction
reaction mechanism
the complete sequence of elementary reactions; the step by step process by which reactants actually become products
under what parameters does an effective collision of reactants occur
they must collide with minimum energy and proper orientation
activation energy
the minimum amount of energy required to start a chemical reaction
endothermic reaction speed
slow, bc requires a higher activation energy
exothermic reaction speed
fast, bc requires lower activation energy
combustion reactions are…
highly exothermic
heat of reaction
- symbol is delta H
- either the overall heat absorbed or released in a reaction
- can be calculated by subtracting the enthalpies of the products - reactants
another word for heat of reaction
enTHALPY
Hess’s Law
the change in enthalpy is the same whether the reaction takes place in one step or a series of steps.
what is the standard heat of energy for elements?
0
an unstable compound will…
break down into simpler substances easily
what table determines compound stability
Table I
what kind of bond is strong?
Exothermic, because prods have low PE
energy of formation
the same as energy of decomposition, but with the reverse sign
reactions that break bonds tend to be _____ at room temperature
slow (endothermic)
aqueous solutions react ____
quickly, the FASTEST kind of reaction is aq + aq
how to increase rate of reaction between gases
increase pressure and thereby decrease volume
ways to speed up reaction rates
- increase concentration
- increase temp (opposite if gas)
- (gas) increase pressure
- increase surface area
catalyst
a catalyst lowers the activation energy in both the forward and reverse reactions equally, providing an ALTERNATE PATHWAY for the reaction
It recombines at the end of the reaction into its own compound again
sometimes causes two Activation Complex’s to form
thermodynamics
allows to prediction of whether a process will occur but gives no info about the amount of time required
delta G
gibb’s free energy change
gibb’s free energy change
change in free energy between reactants and products in their standard state
unit for heat of reaction
kJ/mol or kJ
unit for entropy
kJ per K * mol
unit for gibb’s free energy
kJ/mol r kJ
entropy is an ____ property
extensive, therefore the # of moles must be taken into account
a negative delta G =
spontaneous reaction
what is the formula for gibb’s free energy
G = H - T*S
