3.1.5: Kinetics

Question 1

What is a rate of reaction and how is it calculated?

Answer 1

how quickly something changes
(reactants -> products)

rate of reaction= (reactants used or product produced)/ time

Question 2

What is collision theory?

Answer 2

• in order for atoms to bond, they must collide in the correct orientation with sufficient energy (energy to overcome atom repulsion)
• there needs to be enough energy to overcome atom repulsom
• when bonds break, molecules to deform to rearrange atoms

increasing temperature, increases energy (kinetic)

Question 3

How do you put Relative reaction Rates on a graph?

Answer 3

volume × concentration= where y axis ends
molecule size/ temperature= steepness of the line/ how steep

this is because the larger s.a. of the molecule and higher temperature, the faster the rate of reaction.

Question 4

What is activation energy?

Answer 4

the minimum energy required for a reaction to take place (Ea)

Question 5

What’s an endothermic and exothermic reaction?

Answer 5

Exothermic (-△H)- energy is released in making bonds (more energy in reactants than products)
Endothermic (+△H)- energy is absorbed in breaking bonds (less energy in reactants than products)

BENDy MEXican

Question 6

What do you annotate on an exothermic and endothermic graph?

Answer 6

• reactants
• products
• overall energy change (△H)
• activation energy (Ea)
• transition state
• x= time/ reaction progress
• y= energy

Question 7

What is the highest point on a endothermic/ exothermic graph?

Answer 7

transition state/ active complex
A+B-C–>A-B+C
- reactions occur as when 2 particles approach and the repulsion between atoms causes an increase in potential energy
- all 3 atoms (A,B and C) join by partial bonds and as bond AB forms, BC breaks and potential energy forms

Question 8

What is a rate of Reaction?

Answer 8

How quickly a reaction takes place

rate of reaction= reactants used (or product produced)÷ time

Question 9

What are the different methods to test for rates of reaction?

Answer 9

• collecting gas in a syringe (reduction/ gain oxygen)
• measure change in mass
• pH tracker
• measure concentration change
• measure precipitate formed

÷ time

Question 10

What factors affect rates of reaction?

Answer 10

• concentration
• pressure
• surface area
• temperature
• catalyst

Question 11

How does concentration affect a rate of reaction?

Answer 11

• there is more particles in the same volume (or the reactant than the water)
• more frequent collisions
• however, as the reactants get used up in a reaction, the concentration drops slowing down the rate
• this increases the rate of reaction

Question 12

How does pressure affect a rate of reaction?

gases only

Answer 12

• gas particles are compressed into smaller volume
• more frequent collisions
• this increases the rate of reaction

Question 13

How does surface area affect a rate of reaction?

Answer 13

• more particles exposed at the surface
• so there’s more space for collision to occur between the reactants
• more frequent successful collisions
• this increases the rate of reaction

Question 14

How does temperature affect a rate of reaction?

Answer 14

• particles gain more kinetic energy
• particles move faster so there’s more frequent collisions
• collide with more energy to meet Ea (with frequency and speed)
• this increases the rate of reaction

Question 15

How does the presence of a catalyst affect a rate of reaction?

Answer 15

• creates an alternative reaction pathway
• lowers activation energy
• more particles can react with the same energy (small amount)
• this increases the rate of reaction without getting used up

Question 16

What is the maxwell-boltzman distribution?

Answer 16

• ## shows how speed/ energies of moving molecules vary at different temperatures

Question 17

What is the maxwell-boltzman curve?

Answer 17

• no molecules with 0 energy
• few molecules with high energy
• lower temp.- higher curve, towards left, ends earlier approaching asymptope
• area under graph always the same for each curve though diff. temperatures
• as temp. increases, so does probability of molecules that meet Ea
• adding catalyst lowers Ea
  x axis- energy E

y axis- fraction particles with energy E

Question 18

How do you draw a maxwell-boltzman curve?

Answer 18

• increasing temp. makes molecules on average have more kinetic energy and move faster
• so more molecules have energies greater than Ea
• as molecules have more ke, they collide more frequently
• temperature increasing also increases frequency and energy of molecules
• this increases rate of reaction