unit 4: kinetics

Question 1

factors that affect reaction rates?

Answer 1

physical state
reactant concentration
reactant temp
presence of catalyst

Question 2

how does physical state affect reaction rate?

Answer 2

more readily they collide, the more readily they react.

Question 3

how does reactant concentration affect reaction rate?

Answer 3

more molecules= more reactions

Question 4

how does reactant temp affect reaction rate?

Answer 4

kinetic energy increases with temp. move more quickly = increased frequency of collisions.

Question 5

how does catalyst affect reactant rate?

Answer 5

not involved in overall reaction, affects the kinds of collisions.

Question 6

what is ln2

Answer 6

used to find half life, = 0.693

Question 7

relation of temp and rate?

Answer 7

rate constant (approx. ) doubles with every rise of 10 degrees C

Question 8

what is the collision model?

Answer 8

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.

Question 9

what is activation energy?

Answer 9

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

Question 10

what is transition state

Answer 10

reactants gain energy throughout the reaction, activation energy.

Question 11

what happens at higher energies?

Answer 11

more molecules possess the energy for the reaction to occur. have higher energy than activation energy, meaning the reaction rate increases.

Question 12

higher temp on a graph.

Answer 12

when temp is higher the peak of the graph is lower and to the right a it, smushed.

Question 13

what is a mechanism?

Answer 13

series of stepwise reactions that show how reactants become products. elementary reactions

Question 14

what is required for a successful reaction?

Answer 14

proper orientation and energy.

Question 15

what is an intermediate?

Answer 15

something that is made and immediately reacted.

Question 16

catalysts?

Answer 16

increase rate of reaction, decrease activation energy. don’t get used up, present at beginning and end of reaction

Question 17

homogeneous catalysts

Answer 17

reactants and catalyst are in the same state. usually faster bc they hit each other faster

Question 18

heterogeneous catalysts

Answer 18

diff phase than reactants. often gasses reacting on solid catalyst. often rate determining step

Question 19

enzymes

Answer 19

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.

Question 20

but… how do catalysts work?

Answer 20

provides a different route for a reaction that requires less activation energy

Question 21

how is rate calculated with [ ] and t?

Answer 21

rate = concentration over time. mol/l(s)

Question 22

which step is the rate determining one?

Answer 22

one with the highest activation energy

Question 23

how to calculate rate with balanced equation?

Answer 23

going to/ coming from for your fraction.

Question 24

what is rate law?

Answer 24

R= k [a]^x[b]^y

Question 25

elementary reaction

Answer 25

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.