Rates and equilibria Flashcards
What is the rate of reaction?
How fast a reactant is used up/product formed.
How does rate change over the course of a reaction?
It is fastest at the start as there is a high concentration which slows as the reaction continues. The limiting reactant is fully used up and rate = 0.
What is collision theory?
It states particles must collide with correct orientation and sufficient energy for a reaction to occur and overcome activation energy.
How can the rate of reaction be increased?
- Increase concentration - increase particles in same vol
- Increase pressure - gas compressed increases concentration- closer
- Increase temperature - particles gain KE and have more energy of activation - can react
How can the progress of a reaction be seen?
Decreasing concentration of reactant/increasing concentration of product. If gas is produced, measure the volume of gas at regular intervals OR loss of mass of reactants with balance.
What is a catalyst?
It increase reaction rate by providing an alternative pathway with lower activation energy. Is chemically unchanged/regenerated.
May form an intermediate or provide reaction surface.
What is a homogenous catalyst?
Same physical state as reactants - forms an intermediate.
What are the 2 types of catalysts?
Homogeneous and heterogeneous
What is a heterogeneous catalyst?
Different physical state as reactants.
Usually solids with gas/aq reactants. Reactant adsorbed onto catalyst surface. eg Haber process.
Why are catalysts important?
Economically, increase sustainability as decrease temperature so less energy demand from fossil fuels - less CO2. High atom economy and fewer pollutants.
What does a Boltzmann distribution show?
The distribution in energy of a sample of particles in fluids. Only a small proportion have more than the activation energy to react.
Area under curve shows total number of molecules. No max energy for a molecule and no particles have 0 zero.
What does a Boltzmann look like if temperature increases?
Greater proportion of collisions - greater area to right of activation energy. Wider spread of values. Increase in rate.
What does a Boltzmann look like if a catalyst is used?
More molecules react, so activation energy moves to the left.
What is dynamic equilibrium?
Forward and backwards reactions occur at the same rate in a closed system. No reactants/products can enter/escape.
What is Le Chatalier’s principle?
When equilibrium is subjected to external change, the system reacts in a way to oppose the effect of the change.
