3.1.5 Kinetiks Flashcards
Activation energy
The minimum energy required for a reaction to occur
Why do most collisions not lead to a reaction
Many do not have sufficient energy (activation energy to react)
Collisions may be at wrong orientation to react
Maxwell distribution graph for lower temperature
Curve becomes taller and more compressed, shifting to the left.
Mean energy is less, median energy is less
Activation energy is same
Less particles have activation energy
Area under graph remains constant
What does the area under the Maxwell distribution curve represent?
The number of particles
Maxwell distribution graph for higher temperature
Curve becomes shorter and more stretched, shifting to the right.
Mean energy is more, median energy is more
Activation energy is same
More particles have activation energy
Area under graph remains constant
What are the labels on a Maxwell Distribution Curve
X-axis - Number of particles
Y-axis - Energy
Mean energy
Median energy
Activation energy
Why is median energy less than mean energy on a Maxwell distribution curve
Because often very high energy particles are present, which distort the mean
Rate of reaction definition
The change in concentration of a reactant or product over time.
Effect of temperature on rate of reaction
Particles have more kinetic energy
So collide with more energy
So more frequent successful collisions
So higher rate of reaction
Effect of a catalyst on rate of reaction
M1 provides a different route / mechanism / pathway
M2 with lower activation energy
M3 greater rate of reaction
Effect of increasing concentration on rate of reaction
M1 more particles/molecules in same volume
M2 successful collisions are more frequent
M3 greater rate of reaction
Effect of increasing pressure on rate of reaction
Rate of reaction decreases
Particles are spread further apart
Fewer collisions between gas particles so fewer successful collisions
Catalyst effect on Maxwell distribution curve
Shifts Activation energy left
Explain why a small temperature increase can lead to a large increase in rate
Significantly more molecules have greater energy than the activation energy so can react/collide
Catalyst definition
A substance that increases the rate of a chemical reaction without being changed in chemical composition or amount.
