textbook notes Flashcards
units of k when rate=k
m/s
units of k when rate=k[A]
1/s
units of k when rate=[A][B]
m^-1*s^-1
units of k when rate=[A][B]^2
m^-2*s^-1
activation energy
Collisions must occur with enough energy to allow bondbreaking to occur
The energy threshold that the colliding molecules must exceed in order to react is called the activation energy
If reactant molecules collide with a certain minimum energy, they reach an activated state, from which they can change to product; collisions that occur with an energy below this minimum leave the reactants unchanged
transition state theory
focuses on the high-energy species that exists at the moment of an effective collision when reactants are becoming products
Exists at the highest potential energy
Activation energy of a reaction is used to reach the transition state
reaction mechanism
a sequence of single rxn steps that sum to the overall eqn
small k
if rxn yields little product before reaching equilibrium, we may say there’s “no rxn”
large k
Large K: rxn goes to “completion”
what does Q tell us
Q tells us whether the system has reached equilibrium or, if it hasn’t, how far away it is and in which direction it is changing (for Qc, products in num. and reactants in denom.)
Kp
the equilibrium constant obtained when all components are present at their equilibrium partial pressures
Q<K
shift right
Q>K
shift left
If a rxn has a small K and a large initial reactant concentration or pressure the concentration or pressure change (x) can often be …
neglected
Le Chatelier’s Principle:
if a system at equilibrium is disturbed, it will undergo a change that shifts its equilibrium position in a direction that reduces the effect of the disturbance
Shift to the right: converts reactant to product until equilibrium is reattained
Shift to the left: convert product to reactant until equilibrium is reattained
effect of a change in concentration
When a system at equilibrium is disturbed by a change in concentration of one of the components, it reacts in the direction that reduces the change:
If concentration of A is increased, system shifts right to consume
If concentration of A is decreased, system shifts left to produce
effect of a change in pressure (volume)
If volume decreases(pressure increases), rxn shifts so total number of gas molecules decreases
If volume increases(pressure decreases), rxn shifts so total number of gas molecules increases
effect of a change on in temp
Increase in temp → system shifts in endothermic(heat absorbing) direction to consume added heat → right
Decrease in temp → system shifts in exothermic (heat-releasing) direction to produce more heat → left
Arrhenius acid
substance with H in its formula that dissociated in water to yield H3O+ in water
Arrhenius base
substance with OH in its formula that dissociates in water to yield OH
When an acid and a base react, the H+ from the acid and the OH- from the base form H2O, a process called …
neutralization
proton donor
any species that donates an H+ ion
Must contain H in its formula
proton acceptor
A base is a proton acceptor, any species that accepts an H+ ion
A base must contain a lone pair of electrons to bind H+
All Arrhenius bases contain the Bronsted-Lowry base OH-
Kc for the autoionization of water
Kw- ion-product constant for water
