kinetics

Question 1

what is collision theory ?

Answer 1

• theory that states that reaction only occur there are collisions between particles that have sufficient energy
• this energy is needed to break the relevant bonds in one or either of the reactant molecules

Question 2

What is activation energy ?

Answer 2

• the minimum energy which particles need to start a reaction when they collide

Question 3

Why do most collisions not lead to a reaction ?

Answer 3

• because the particle colliding do not have the sufficient energy needed to start the reaction

Question 4

What does a Maxwell-Boltzmann distribution show ?

Answer 4

• shows the spread of energies that molecules of gas or liquid have at a particular temperature in a closes system

Question 5

How can a reaction be completed if only a few particles have energy greater than the activation energy ?

Answer 5

• particles can gain energy through collisions

Question 6

What is the rate of reaction

Answer 6

• defined as the change in concentration of a substance in a unit of time
• mol dm^-3 ^-1

Question 7

How do you find the rate of reaction a graph of concentration plotted against time ?

Answer 7

• find the gradient

Question 8

What is the initial rate of reaction ?

Answer 8

• the rate at the start of the reaction where the rate is the fastest

Question 9

In the experiment of sodium thiosulfate and hydrochloric acid, why do we measure the reaction rate of 1/time

Answer 9

• we are no including the concentration and we can assume the amount of sulfur produced is fixed and constant

Question 10

What is the effect of increasing the temperature on the rate of reaction ?

Answer 10

• a higher temperature means the particles have more energy
• more particles have energy greater than the the activation energy so the is a higher frequency of successful collisions
• so a higher rate of reaction

Question 11

What is the effect of increasing the surface area on the rate of reaction ?

Answer 11

• higher surface ares means successful collisions will occur more frequently
• which increases the rate of reaction

Question 12

What is the effect of increasing the concentration and pressure on the rate of reaction ?

Answer 12

• higher concentration and pressure means more particles per unit of volume
• so higher frequency of particles colliding
• therefore higher frequency of effective collisions
• doubling the concentration means double the amount of particles per unit of volume

Question 13

What do catalyst do ?

Answer 13

• increase the rate of reaction without being used up
• by providing an alternative route or mechanism which requires a lower activation energy

Question 14

What is the effect of catalysts on the rate of reaction ?

Answer 14

• more particles will have energy greater than the activation energy
• as the activation energy is lower
• so more successful collisions
• so the rate of reaction will increase