rates of reactions

Question 1

what must occur for a reaction to be said to have happened?

Answer 1

• activation energy is absorbed to break reactant binds (intramolecular) ensuring that atoms are free to rearrange themselves
• the atoms to rearrange themselves need to come into contact (collisions)

Question 2

what is a successful collision?

Answer 2

• atoms collide
• collide with sufficient energy to overcome activation energy
• collide with correct orientation (correct atoms to make compound)

Question 3

how is collision theory extended?

Answer 3

to describe rate of reaction

Question 4

what is it important to reference when describing the rate of a chemical reaction?

Answer 4

the reaction over a set period of time- how collisions are impacted to speed up a reaction

Question 5

collision are more likely…

Answer 5

more successful rate of reaction

Question 6

collisions less likely…

Answer 6

less successful rate of reaction- slow

Question 7

in a graph of rate…

• the steep bit
• the plateau

Answer 7

• steep: fast rate of reaction

- flat: reaction is over

Question 8

does the amount of product possibly made stay the same when altering rate of reaction?

Answer 8

yes, if the reactant amount is the same

Question 9

how does concentration affect rate of reaction (collisions)?

Answer 9

• increased, there is an increased chance of successful collisions, therefore the rate of reaction increases
• when decreased, there is a decreased chance of collisions and therefore the tae of reaction decreases

Question 10

how does surface area affect the rate of reactions (collisions)? when is surface area increased? when is the surface area decreased?

Answer 10

• chemical reactions (collisions) occur at the surface of a chemical
• surface area is increased when more surface is exposed- powdered, fine granules, crushed
• when less surface is exposed- pellet, solid, granule
• when SA is increased, there is an increased likelihood of successful collisions and this translates into increased rate. (the opposite is true)

Question 11

how does temperature affect the rate of reactions (collisions)?

Answer 11

• increased, therefore increased kinetic energy in particles so there is an increased chance of successful collisions and therefore an increased chance of collisions
• decreased, decreased kinetic, decreased successful collisions, decreased rate

Question 12

what is a catalyst?

Answer 12

a chemical substance that is not consumed by a chemical reaction

• some are specific to certain chemicals
• biological catalysts are called enzymes and are reliant on optimum conditions of pH and temp. If wrong, they may denature
• chemical substances do not denature but become contaminated

Question 13

how do catalysts function to speed up reactions?

Answer 13

• provide an alternative energy pathway

- lower the activation energy to ensure less energy is needed to disrupt reactant bonds and get reactions started

Question 14

how do catalysts specifically work?

Answer 14

their energy conservation functions to increase thermal energy, increasing kinetic energy, moving particles more and therefore increasing chance of collisions and therefore increasing rate of reaction

Question 15

what are the two types of catalysts?

Answer 15

homogenous: present in same state as the reactants
heterogenous: present in different state to reactants