Kinetics Flashcards
(22 cards)
What are the requirements for a reaction to take place (3)
The particles must collide
The particles must have enough energy for the collision to break the bonds (activation energy)
They must collide in the correct orientation
What factors affect the rate of reaction (3)
Increasing the concentration of reactants increases the frequency that they collide
Increasing the gas pressure means the particles are closer together so collide more frequently
Increasing the temperature gives the particles more kinetic energy so they move faster and collide more frequently with more energy
How do you measure the rate of reaction on a graph?
Draw a tangent to the point you want to measure then work out the gradient (change in y over change in x)
What is the definition of activation energy?
The minimum amount of energy required for particles to start a reaction by breaking chemical bonds
What do catalysts do?
They allow a reaction to take place via an alternative pathway using a lower activation energy
What are 2 features of a catalyst?
They are not used up or permanently changed
They make reactions require less energy so are more environmentally friendly but can be toxic
What happens to a Maxwell-Boltzmann curve when you increase the temperature?
The curve shifts to the left and flattens a bit
Where is the mean energy in proportion to the most probable energy?
It is to the left of it because molecules with very high amounts of energy skew it
What is a reversible reaction?
When products can be converted back to reactants
What is a closed system?
When no atoms can enter or leave the system
What is equilibrium?
When the concentrations of products and reactants remain constant (do not have to be the same amount)
What is Le Chateliers Principle?
When an external change is applied to a system at equilibrium, the equilibrium moves in the direction that reduces the effect of that change
What happens to the equilibrium position in the concentration of one side in increased?
The rate of reaction moving away from that side increases to reduce the concentration of the increased side- it stops when it has achieved this
What happens to the equilibrium position when the pressure of the system in increased?
It will move towards the side that has less moles
What will happen to the equilibrium position when the temperature of the system in increased?
It will move in the endothermic direction (the direction that decreases the temperature)
What will happen to the equilibrium position if you add a catalyst?
It will increase the rate of the forwards and reverse reactions equally so the position will not change but the reaction will reach equilibrium faster if the catalyst is added before that happens
What is the equilibrium constant?
The amount of products and reactant present at equilibrium
How do you calculate the equilibrium constant?
Concentration of products to the power of their balancing numbers over concentration of the reactants to their balancing numbers
How do you calculate the units of the equilibrium constant?
Replace the concentrations in the equations with moldm-3 and cancel out to get your answer
How do you interpret the calculated equilibrium constant?
If Kc is less than one then the equilibrium lies towards the reactants,
If Kc is equal to one then the equilibrium lies midway,
If Kc is greater than one then the equilibrium lies towards the products,
Why can a small temperature change lead to a large increase in reaction rate?
Shifts the curve to the right which has a big effect on the amount of particles with the minimum activation energy which can increase rate of reaction
What is a catalyst?
A substance that provides an alternate reaction pathway and is not used up/ damaged in the process
