Module 3 Chapter 10 Flashcards
What is rate of reaction
A measure of how quickly a reaction occurs.
What are the three ways to calculate rate of reaction
Rate of reaction = mass of product produced / time
Rate of reaction = mass of reactant used / time
Reaction rate = change in concentration / time
What is the graph of concentration against time for the products and reactants of a reaction
DRAW IT
What does this graph show us
That the initial rate of reaction is the highest.
Reaction rate decreases the longer the reaction goes.
When 1 of the reactants run out there will be no further reaction.
What are the 5 ways that rate of reaction can be changed
Concentration of reactants
The temperature
Surface area
Pressure (for gases)
Catalysts
What are the three factors needed for a successful collision/ reaction
The particles need to have sufficient energy (activation energy)
The particles have to collide
The particles should be in the correct orientation
What is the effect of increasing concentration of reactants on rate of reaction and why
Increasing the concentration of solution will increase the rate of reaction. As there are more reactant particles in a given volume, allowing for a higher frequency of collisions and therefore successful collisions.
What has the same effect as increasing the concentration of the reactants
Increasing the pressure for gases
What is the effect of decreasing concentration of reactants on rate of reaction and why
Decreasing the concentration of solution will decrease the rate of reaction. As there are less reactant particles in a given volume, resulting in a lower frequency of collisions and therefore successful collisions.
What is the effect of increasing the temperature of the reactants on the rate of reaction
If you increase the temperature of the reactants a higher proportion of the reactants have the activation energy or more this results in an increase in the frequency of successful collisions resulting in an increased rate of reaction. An increase in temperature also means that the reactants have a greater kinetic energy leading to an increase in the frequency of collisions and successful collisions resulting in a greater rate of reaction.
What is the effect of decereasing the temperature of the reactants on the rate of reaction
If you decrease the temperature of the reactants a lower proportion of the reactants have the activation energy or more this results in a decrease in the frequency of successful collisions resulting in a decreased rate of reaction. A decrease in temperature also means that the reactants have a lower kinetic energy leading to an decrease in the frequency of collisions and successful collisions resulting in a lower rate of reaction.
What is the impact of increasing the surface area to volume ratio on rate of reaction
If you increase the surface area to volume ratio more reactant particles are available for collision, collisions are more likely, leading to a greater frequency of collisions and therefore an increase in rate of reaction.
What is the impact of decreasing SA:VOL ratio on rate of reaction
If you decrease the surface area to volume ratio less reactant particles are available for collision, collisions are less likely, leading to a lower frequency of collisions and therefore an decreased in rate of reaction.
What is the effect of catalysts on rate of reaction
Catalyst increase the rate of chemical reactions, by lowering the activation energy providing another reaction pathway. So a greater proportion of the particles have the activation energy or more resulting in a greater rate of reaction.
What happens during a chemical reaction
New product formed
Fizzing/ effervescence / gas given off
Colour change
How can these changes be used to measure rate of reaction
Measure the volume of gas produced in a given time using a gas syringe or upturned cylinder.
Measure the change in mass over time.
Measure how long it takes for a cross to disappear.
At what time is the initial rate of reaction measured
It is measured at t = 0
How are instantaneous rates of reaction measured
A tangent to the curve at that time is drawn and then using the tangent a gradient is calculated to work out rate of reaction.
What is a catalyst
A substance that changes the rate of a chemical reaction without undergoing any permanent change itself.
What is a feature of a catalyst
They are not used up during a reaction
What may catalyst do
They may react with a reactant to form an intermediate ( a species formed during a reaction that reacts further and is not present in the final products) or may provide a surface on which the reaction can take place.
What happens to catalysts at the end of a reaction
They are regenerated
What are the two types of catalyst
Homogenous catalysts : is in the same physical state as the reactants it reacts with
Heterogenous catalyst : is in a different physical state to the reactants it reacts with
When catalysts provide a surface for the reaction to take place on what are the order of events and there names
Adsorption - weakly bonded onto the surface of catalyst
Reaction
Desorption - after reaction product molecules are released
What are some examples of catalyst in real life
Platinum and palladium catalyst are used in catalytic converted of cars where harmful gases are turned into harmless gases.
Enzymes are biological catalysts.
What are enzymes
Large protein molecules that are specific to a substrate and a reaction. There active site is keyed to that molecule.
What are enzymes important for
Pharmaceutical development
How can enzymes be effected by PH and temperature
DRAW THE GRAPHS
What happens past the conditions that an enzyme is meant to work out
The enzyme can denature
What is autocatalysis
The process by which the product of a reaction acts as a catalyst for the reaction itself.
What are the benefits of using a catalyst
Activation energy lowered, which means less energy is needed in the reaction to take place
Therefore lower temperatures can be used which saves money and resources
More profit and less harmful effects of energy generation
Draw a Boltzman’s distribution curve
What is assumed in a Boltzmann’s distribution
All collisions between particles and the surface of the container are elastic
(a collision in which there is no loss of kinetic energy in the systems as a result of the collision)
Draw a Boltzmans’ distribution with an increase in temperature
What does the area under the curve represent
The total number of molecules
Therefore when temperature increases what has to stay the same and what does it cause the curves to do
The area has to remain the same.
So the peak gets lower as the curve shifts to the right.
Draw a Boltzman’s distribution for a lower temperatures
Draw a Boltzman’s distribution for the presence of a catalyst
Why does the Boltzman’s distribution height decrease and curve shift to the right when temperature increases
More molecules have an energy that is greater than the activation energy. Therefore the curve has shifted to the right, however, the height of the curve decreases as the number of molecules stays the same which is represented by the area under the curve.
Why does the activation energy shift to the left in the presence of a catalyst in the Boltzman’s distribution curve.
A catalyst provides an alternative reaction route with a lower activation energy. As a result the activation energy shifts to the left and a higher proportion of the particles have the activation energy required or more.
What symbol represents the reversible reaction is at equilibrium
DRAW IT
Draw a graph of percentage of reactants and products against time
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On the graph when is dynamic equilibrium reached
When both reactions occur at the same rate, the amount of reactant and products stays the same.
What is dynamic equilibrium
. Closed system
. There are 2 reactions occurring at the same time the forward and backward reaction
. The relative amount of products and reactants stays the same. The conditions can change the amounts
. The rate of the forward and back award reaction are the same therefore it appears that no further reaction takes place
What is le chateliers principle
When a change is made to a reaction at equilibrium, the position of equilibrium moves to oppose the change.
Why does le chateliers principle exist
Whatever, you do to the reaction, the reaction will do the opposite as at equilibrium is most stable and existing at lowest energy.
What happens if concentration increases
If a concentration of a substance increases, the equilibrium position moves in the direction away from that substance.
What happens when you change temperature
If temperature increases, the equilibrium position moves in the direction of the endothermic change.
What happens when you change pressure
When the pressure is increased, the equilibrium position moves in the direction of the fewest moles.
What effect do catalyst have on equilibrium position
They do not have an effect on equilibrium position
What is the formula for Kc
Kc = concentration C ^mol C x concentration D ^mol D/ concentration A ^mol A x concentration B ^mol B
If Kc = 1 what does it mean
The position of equilibrium is halfway between the reactants and products.
If Kc > 1 what does this mean
the position of equilibrium is towards the products
What if Kc < 1
Indicated that the position of equilibrium is towards the reactants.
As the Kc value gets larger
The further the position of equilibrium lies to the right of the products
As Kc gets smaller what occurs
The position of equilibrium lies further to the left of the reactants
