unit 4: kinetics Flashcards
factors that affect reaction rates?
physical state
reactant concentration
reactant temp
presence of catalyst
how does physical state affect reaction rate?
more readily they collide, the more readily they react.
how does reactant concentration affect reaction rate?
more molecules= more reactions
how does reactant temp affect reaction rate?
kinetic energy increases with temp. move more quickly = increased frequency of collisions.
how does catalyst affect reactant rate?
not involved in overall reaction, affects the kinds of collisions.
what is ln2
used to find half life, = 0.693
relation of temp and rate?
rate constant (approx. ) doubles with every rise of 10 degrees C
what is the collision model?
bonds are broken and new bonds are formed in a reaction
molecules can only react if they collide with each other, but they can collide and not react If they’re not properly aligned.
what is activation energy?
the small amount of energy needed to have a reaction make place. the point where its least stable. minimum energy needed to get molecules to transition state is activation energy
what is transition state
reactants gain energy throughout the reaction, activation energy.
what happens at higher energies?
more molecules possess the energy for the reaction to occur. have higher energy than activation energy, meaning the reaction rate increases.
higher temp on a graph.
when temp is higher the peak of the graph is lower and to the right a it, smushed.
what is a mechanism?
series of stepwise reactions that show how reactants become products. elementary reactions
what is required for a successful reaction?
proper orientation and energy.
what is an intermediate?
something that is made and immediately reacted.
catalysts?
increase rate of reaction, decrease activation energy. don’t get used up, present at beginning and end of reaction
homogeneous catalysts
reactants and catalyst are in the same state. usually faster bc they hit each other faster
heterogeneous catalysts
diff phase than reactants. often gasses reacting on solid catalyst. often rate determining step
enzymes
biological catalysts. active site where reactants attach, reactants are referred to as substrates. sometimes its a lock and key model, very specific shape for both. happens very fast.
but… how do catalysts work?
provides a different route for a reaction that requires less activation energy
how is rate calculated with [ ] and t?
rate = concentration over time. mol/l(s)
which step is the rate determining one?
one with the highest activation energy
how to calculate rate with balanced equation?
going to/ coming from for your fraction.
what is rate law?
R= k [a]^x[b]^y
elementary reaction
elementary reaction is a chemical reaction in which one or more chemical species react directly to form products in a single reaction step and with a single transition state.
