3.2.2 Reaction Rates Flashcards
Effect of concentration on rate of reaction
If concentration increases, so does rate of reaction
Increases number of particles in the same volume, particles are closer together and collide more frequently, more frequent successful collisions
Effect of pressure of a gas on rate of reaction
When pressure increases, so does rate of reaction
Concentration of gas molecules increases as same no of molecules occupy a smaller volume, molecules closer together and more frequent collisions, so more successful collisions
Reaction rate equation
Rate = change in conc ÷ time
What do catalysts do
Increase reaction rate without being used up
How do catalysts increase reaction rate
Providing an alternative reaction pathway of lower activation energy
What is a homogenous catalyst
A catalyst with the same physical state as the reactants
What is a heterogenous catalyst
Catalysts with a different state to the reactants
How are catalysts important in industry
Catalysts increase rate by lowering activation energy which reduces temperature needed and energy requirements
Less electricity/ fossil fuels used, cuts costs and increases profitability, economic advantage
Using less fossil fuels cuts CO2 emissions, and less use of a finite resource, sustainable advantage
What does Boltzmann distribution show
Spread of molecular energies in gases, shows proportion of molecules with enough energy to overcome activation energy
Features of Boltzmann distribution
No molecules have 0 energy
Area under curve is equal to total number of molecules
No max energy
Effect of temperature on Boltzmann distribution and why
At a higher temperature the peak is lower and shifted to the right, greater proportion of molecules overcome AE
More molecules have energy greater than or equal to activation energy
Therefore greater proportion of collisions would lead to reaction, increases rate of reaction
Effect of catalysts on Boltzmann distribution
Provides alternative reaction route with lower AE, greater proportion of molecules have energy equal to/ greater than AE
More molecules collide and react to form products, increased rate of reaction
How to determine rate of reaction via monitoring volume of gas produces
Conical flask with reactants, delivery time to upturned measuring cylinder placed in a trough with water
Decomposition of H2O2
Record initial volume of gas in measuring cylinder
Add manganese dioxide catalyst to conical flask, start stop clock
Record volume in measuring cylinder at regular intervals
Plot of volume and time, calculate initial rate with tangent
How to determine rate of reaction via loss of mass of reactants
Rate of reaction between calcium carbonate and HCl
Add both to conical flask on a balance, mass recorded initially
Record mass at regular time intervals
Plot graph of mass lost against time
Calculate rate by drawing tangent
X axis of Boltzmann distribution
Energy
