C10- Rates of Reaction and Equilibrium Flashcards
(30 cards)
What is meant by rate of reaction
How fast a reactant is being used up
How fast a product is being formed
Change of concentration in a product or reactant in a given time
Simple equation for rate of reaction
Change in concentration/ time
4 variables that affect the rate of a reaction
Concentration (or pressure for gases)
Temperature
Use of catalyst
Surface area of solid reactants
Two conditions of an effective collision
Particles collide with the correct orientation
Particles collide with enough energy to overcome the barrier of the activation energy
Why does rate of reaction increase when concentration increases
Particles are closer together so collide more frequently
More particles in the same volume
More effective collisions in a set period of time
Why does increasing the pressure of a reaction increase its’ rate
Concentration of gaseous molecules will increase
Gas particles are closer together and collide more frequently
Leads to more effective collisions in a set period of time
Methods for following the progress of a reaction
Monitoring the removal of a reactant
Monitoring the formation of a product
How to measure the progress of a reaction that produces gas
Monitoring the volume of gas produced at regular intervals
Measuring the loss in mass of the reactants using a balance
Define catalyst
A catalyst is a substance that changes the rate of a chemical reaction without undergoing a permanent change itself
increases rate of reaction though providing an alternative reaction route of a lowered activation energy
3 key characteristics of a catalyst
The catalyst is not used up in a chemical reaction
Catalyst reacts to form an intermediate or provide a surface for the reaction to take place
At the end of the reaction the catalyst is regenerated
Define homogeneous catalyst
A catalyst that ahs the same physical state as the reactants
Define heterogeneous catalyst
Catalyst has a different physical state from the reactants
How does a catalyst work
bonds formed
reactant molecules are adsorbed (weakly bonded) onto the surface of a catalyst where the reaction takes place
After the reaction, the product molecules leave the catalysts surface by desorption
Why use a catalyst in industry
Reduces temperature needed for a reaction
Thus uses less energy
Cuts costs and makes reaction more profitable
Economic costs of catalyst outweigh the costs associated with developing a catalytic process
3 key features of a boltzmann distribution
No molecules have zero energy, the curve starts at the origin
Area under the curve is equal to the total number of molecules
No maximum energy for a molecule, the curve never meets the x axis
Effect of temperature on the boltzmann distribution
more molecules have an energy greater than or equal to he activation energy
therfore a greater proportion of collisions lead to a reaction
increases rate
Effect of a catalyst on a boltzmann distribution
A catalyst provides an alternative reaction route with a lower activation energy
A greater proportion of molecules now have an energy equal to or over the activation energy
upon collision, more molecules will react to form products
What does the area under a boltzmann distribution represent
Total number of particles
Effect of a temperature increase on the start and end points of a boltzmann distribution
Curve always starts at the origin as the molecules have no energy
Both curves will never touch the x axis as very few but not zero particles have energies this high
2 characteristics of a reversible reaction that is in equilibrium
Rate of the forward reaction is equal to that of the reverse
The concentration of reactants and products do not change
What is a closed system
equilibrium
A system that is isolated from its surroundings
Therefore temperature pressure and concentrations of reactants and products remains unaffected by outside influences
General le chateliers principal
When a system in equilibrium is subjected to external change the system readjusts itself to minimise the effect of the change
Effect of concentration of the position of equilibrium
If more products are formed (their conc inc) then equilibrium shift s to the right
If more reactants are formed (Inc conc) then the equilibrium shifts to the left
Example reaction to demonstrate the effect on concentration on the position of equilibrium
Reaction from chromate to dichromate ions
Solution turn from yellow to orange as concentration of H+ ion sin products or reactants increases
