Kinetics Flashcards
How can a reaction go to completion if few particles have energy greater than Ea?
Particles can gain energy through collisions.
Definition of activation energy
The minimum amount of energy particles require to collide and start a reaction.
Why do most collisions not lead to a reaction?
Not enough energy gained through collision, I.E incorrect orientation and energy not past Ea.
What is the rate of a reaction defined as?
The change in concentration of a substance in unit time.
What is the effect on the rate of reaction at higher concentrations and volumes?
More particles per unit volume
Particles collide with a greater frequency
Higher frequency of effective collisions
What happens if we double the conc.?
Double the particles per unit volume and double the frequency of effective collisions
Effect of increasing concentration on curve
Shape of energy distribution curve does not change
Curve will be higher and area under curve will be greater because more particles
The higher the concentration/temperature/surface area…
The faster the rate (steeper gradient)
What is the effect of increasing temperature ?
The energy of the particles increases
Particles collide more frequently and more often with energy greater than the Ea. More collisions result in a reaction.
What is the effect of increase in temperature on the graph?
Bigger proportion is particles have energy greater than the Ea, so the frequency of the successful collisions increases.
What is the effect of increasing surface area? What would be the effect of breaking a big lump into smaller pieces.
It will cause successful collisions to occur more frequently between the reactant particles, increasing the rate of reaction. Breaking into smaller pieces would increase the rate of the reaction
What is a catalyst?
Explanation
They increase the rate of reaction without being used up.
They provide an alternative route with a lower Ea.
What is the effect of a catalyst on a reaction
Lowers the Ea
More particles will have energy greater than Ea so there will be a higher frequency of effective collisions.
Therefore reaction will be faster
At higher temperatures the peak of the curve…
Is lower and moves to the right
Rate invp. [X][Y]
What is the effect of X and Y in the rate?
What would happen if we doubled any of them?
The effect of X and Y are equal
Doubling X or Y would double the rate of the reaction.
Doubling the conc. both would quadruple the rate
Rate invp. [X][Y]^2
What would be the effect of doubling X? And Y?
Doubling X would double the rate
Double Y would quadruple the rate
What can the order of the reaction be determined by? What about the overall order?
The power by which the conc of that specie is raised to in the rate equation.
It can be determined by summing all the orders.
What is the order of a specie that does not affect the rate?
0 order
If the rate graph is a straight horizontal line…
If the rate graph is a sloping straight line…
If the graph is not a straight line…
… the order is zero (the concentration of this species has no effect on rate)
… the order is one
… the order cannot be found directly, it could be 2 so try plotting against [A]^2
For every how many kelvin does the rate double? When is this applicable?
Every 10K rise
When the Ea is roughly 50kJ/mol and around room temperature
The slowest step may form a…
Bottleneck called the rate determining step
What reactions would determine the rate determining step
The reaction before the slowest reaction and the slowest reaction itself
