A4 kinetics 1 Flashcards
Describe how decreasing concentration affects rate
Decreases rate
Less particles per unit volume
Less frequent collisions
Less successful collisions per unit time
Describe how increasing concentration affects rate
Increases rate
More particles per unit volume
More frequent collisions
More frequent collisions per unit time
Describe how increasing pressure affects rate
Increases
more particles per unit volume
Increases the concentration of molecules
collision freqeuncy is higher
More successful collisions per unit time
Describe how decreasing pressure affects rate
Decreases rate
Decreases the concentration of molecules
Less frequent collisions
Less successful collisions per unit time
Describe how increasing temperature affects rate
Increases rate
Particles have more kinetic energy
More particles have energy greater than the activation energy
More successful collisions per unit time
Describe how decreasing temperature affects rate
Decreases rate
Particles have less kinetic energy
Less particles have energy greater than the activation energy
More successful collisions per unit time
Describe a method to calculate initial rate
Plot a XXX against time graph
Draw a tangent at t=0s
Gradient of tangent = XXX/Time
Gradient of tangent = initial rate
Define a catalyst
Lowers activation energy of reaction
By providing an alternative route for the reaction
Meaning a greater number of molecules have energy that’s greater than the activation energy
Describe the difference between homogenous and heterogenous catalysts
Homogenous catalysts are in the same physical state as the reactants
Heterogenous catalysts are in a different physical state to the reactants
When is it difficult to classify if a catalyst is homogenous or heterogenous
When the reactants have different physical states
Describe and explain the importance of catalysts
Allow reactions to occur at lower temperatures
Reduce energy demand from combustion of fossil fuels
Less CO2 produced
Describe the apparatus and method to investigate rate with volume
Weigh excess metal using mass balance
Measure volume of acid using measuring cylinder
Mix metal and acid in conical flask
Measure gas volumes from gas syringe at regular intervals
Example: 15s using stopwatch
Continue until no further change in volume
Describe the apparatus and method to investigate rate with mass
Weigh excess mass of metal using mass balance
Measure volume of acid with measuring cylinder
Mix metal and acid in conical flask
Measure initial mass
Re-weigh at regular time intervals
Example: 15s using stopwatch
Continue until no further change in mass
Draw a Maxwell-Boltzmann graph, and show and explain how an increased temperature would affect this
Increasing temperature means that there is a greater area under the curve above the activation energy
A greater number of molecules have energy greater than the activation energy
Describe and show how a catalyst affects a Maxwell-Boltzmann distribution graph
Greater area under the curve with energy above the activation energy
A greater number of molecules have energy greater than the activation energy
boltsmzan distribution effect of catlaisted reaction
activation energy shifts to left
explain how increase temp on Boltzmann
more particles have at least the activation so they have enough ernegy to collide and react
rate equation
change in conc/ time
rates units
mol dm -3 s-1
alternating rate of chemical reaction factors
conc
temp
catalyst
surface area of solid reactants
tangent
gradient rise/ run
finds rate of reaction
collision theory
reacting particles must collide for a reaction to occur
collisions to be effective
particles collide with correct orientation
Particles have sufficient energy to overcome the activation energy barriers of the reaction
higer solid SA increases rates because
more of solid is exposed to other particles
so collision frequency is higher
so there are more successful collisions per unit time
rate of chemical reaction def
measure of how fast a reactant is being used up or how fast a product is formed
