24:Rates Flashcards
What is the rate of a reaction
Rate of change of the concentration of a reactant or product with time
What are the units for rate of reaction
moldm¯³s¯¹
How could you measure the rate of reaction practically
Measure the change in mass as a function of time.
Volume of gas produced as a function of time.
Measure pH as function of time
What does rate of reaction depend on (collision theory)
Frequency of collisions and probability that the collision is successful
Why does an increase in concentration increase the rate of reaction
Particles are closer to each other so collide more frequently
What is activation energy
The minimum amount of energy required for a reaction to occur when particles collide
Describe the enthalpy profile diagram for an exothermic reaction
The reactants are higher than the products so Δh is negative
Describe the enthalpy profile diagram for an endothermic reaction
The reactants are lower than the products so Δh is positive
Why does raising the temperature increase rate of reaction
Increases the proportion of molecules that have an energy greater than Ea. So it is more likely that a collision is successful.
Molecules move faster on average so collide more frequently.
How to show increase in temperature on Boltzmann distribution
A higher proportion of the molecules have more energy than Ea. so there is more on the right of the diagram.
How does a catalyst increase rate of reaction
Provides an alternative pathway with lower activation energy.
How can the effect of a catalyst be shown on the boltzmann distribution
The Ea will be lower (further to the left)
What is a homogeneous catalyst
Catalyst is in the same phase as the reactants
What is a heterogeneous catalyst
The Catalyst is in a different phase from reactants
Why are catalysts important for industrial chemistry in terms of economy and sustainability
Reaction can operate at lower temperatures so less fuel is needed: cheaper and produces less CO₂
