Ch. 10 Flashcards
Reacting molecules must collide, have a minimum amount of ____, and have _____ orientation to form products
energy
proper
Three conditions required for a reaction to occur
- Collision
- Orientation (proper alignment to break & form bonds)
- Energy (of activation)
The ____ ____ is the minimum amount of energy needed to convert the colliding molecules into product
activation energy
rate of reaction =
change in concentration of reactant or product / change in time
Factors that affect the rate of a reaction
- temp change
- concentration
- adding a catalyst
reactions with ____ activation energies go faster than reactions with ____ activation energies
low
high
at higher temps, increase in KE of reactant molecules
makes them move faster
makes them collide more often
makes them collide with more energy
For every ___ increase in temperature, most reaction rates will _____
10 deg C; double
increase reacting molecules will cause more collisions and form more products so
reaction goes faster
catalysts speeds up the rate of reaction by providing an alternative pathway that
has a lower activation energy
during a reaction, a catalyst is…
not changed or consumed
when activation energy is lowered, more collisions provide energy for
reactants to form a product
refer to table 10.1
sweet job nerd
in most chemical rxns, reactants are not completely converted to products because
a reverse reaction takes place in which products collide to form the reactants
when a reaction proceeds in both a forward and a reverse direction, it is said to be a
reversible reaction
occurs in both the forward and reverse direction at the same time
reversible reaction
has two rates, a rate for the forward reaction and a rate for the reverse reaction
reversible reaction
as the reaction progresses, the rate of forward rxn decreases and that of the reverse rxn ___
increases
at equilibrium the rates of the forward and reverse reactions are _____
equal
the rate of the forward rxn = rate of reverse rxn AND
forward and reverse rxn’s continue at same rate
equilibrium
products form reactants in the ____ reaction
reverse
reactants form products in the ___ reaction
forward
Equilibrium constant
multiplies the concentrations of the products together and divides by the concentrations of the reactants (products) / (reactants)
Kc value is the
equilibrium constant
know what to find the Kc value from an equilibrium expression for a reaction
slide 30
a reaction at a specific temperature can have only
one value for the equilibrium constant
does size of the equilibrium constant affect how fast the equilibrium is reached?
NO, size of Kc does not affect how fast equilibrium is reached
small Kc means…..
mostly reactants (little reaction takes place)
large Kc means…
mostly products (reaction essentially complete)
Kc close to 1
moderate reaction
states that when a stress is placed on a reaction at equilibrium, the system responds by changing the rate of the forward or reverse reaction in the direction that reverses stress
La Chatelier’s principle
If some of the reactant is removed, the rate of ___ reaction increases to form more ___ until equilibrium is reached
reverse; reactant
i.e. equilibrium shifts towards reactants
Table 10.4 - look at it
Way to go bro
Adding a catalyst does not change equilibrium (T/F)?
True
adding a catalyst speeds up a reaction by lowering activation energy, thus increasing the rate of the ____
forward and reverse reactions
time to equilibrium shorter with a catalyst, but ratios of reactants and products
does not change
the rate of a reaction is the speed at which….
reactants are consumed or products are formed
at higher temperatures, reaction rates ____ because reactants move faster, collide more often, and produce more collisions, which have the required
increased
energy of activation
effect on rate of chemical reaction: adding a catalyst
increase
effect on rate of chemical reaction: running the reaction at a lower temperature
decrease
effect on rate of chemical reaction: doubling the concentrations of the reactants
increase
effect on rate of chemical reaction: removing a catalyst
decrease
effect on rate of chemical reaction: running the experiment under the same conditions in a different lab
no change
effect on rate of chemical reaction: increasing the temperature
increase
effect on rate of chemical reaction: using lower concentrations of reactants
decrease
look at learning exercise 10.1B
well done dorkus
indicates that a reaction takes place only when molecules collide with the proper orientation and sufficient energy
collision theory
the minimum energy required to break the bonds between atoms of the reactants
activation energy
the conditions required for a reaction to occur
- collision - the reactants must collide
- orientation - the reactants must align properly to break and form bonds
- energy - the collision must provide the energy of activation
rate of reaction =
change in concentration of reactant or product / change in time
Factors that increase reaction rate?
increasing temp - more collision with energy of activation
increasing reactant concentration - more collisions
adding a catalyst - lowers activation energy
for every 10 deg celsius increase in temperature….
the reaction rates approximately double
another way to speed up a reaction is to lower the ….
energy of activation (catalyst does this)
Kc =
[products] / [reactants]
Large Kc?
Mostly products (reaction essentially complete)
Small Kc?
mostly reactants (Little reaction takes place)
Kc close to 1?
Reactants almost equal to products (moderate reaction)
When a stress (change in conditions) is placed on a reaction at equilibrium, the equilibrium will shift in the direction that relieves stress
La Chatelier’s Principle
chemical equilibrium occurs in a reversible reaction when….
the rate of the forward reaction = rate of reverse reaction
at equilibrium ___ change in the concentrations of the reactants and products as the forward and reverse reactions continue
no further
increasing the temperature of an endothermic reaction or decreasing the temperature of an exothermic reaction will cause the system to
shift in the direction of the products
an increase in the volume of the container causes a shift in the direction of the reaction with
more moles of gas (not solids so keep an eye out for reactions that have solids… also solids are not put into the Kc equation)
