2.2 Rates Of Reaction Flashcards
What is collision theory
Reactant particles must collide with correct orientation and have activation energy
Define activation energy
Minimum amount of energy required for a reaction to take place between 2 particles.
How do you calculate rate
Amount of reactant used/product formed/ time (s)
What are the factors affecting rate of reactions
concentration, pressure, particle size , temperature, catalysts and light
How does temperature affect rates of reaction
There will be an increase in kinetic energy of the molecules and so they will move faster, so more molecules have enough energy to react on collision meaning the rate will increase so more effective collisions.
How does particle size affect rate of reaction
Reducing particle size of a solid increases surface area so molecules are closer together and there is an increase in the number of collisions per unit time leading to an increase in reaction rate
How does catalyst increase the rate of reaction
By providing a different pathway for the reaction that has a lower activation energy
How does concentration affect rates of reaction
At higher concentrations, there are more reacting particles in the same volume so there are more frequent successful effective collisions
How does pressure affect rate of reaction
More reacting particles in the same volume of gas so more frequent successful collisions
Define catalyst
substance that speeds up the rate of a chemical reaction without being chemically changed at the end
What is a homogenous catalyst
a catalyst that is in the same phase as all the reactants. They take an active part in a reaction rather than being an inactive spectator.
Typically involves liquid mixtures or substances in solution eg concentrated sulphuric acid
What is a heterogenous catalyst
In a different phase from the reactants.
Many heterogenous catalysts are d block transition metals
How can you measure a rate of reaction when a gas is given off
Collect gas produced in an upside down measuring cylinder in a trough of water or in gas syringe to measure the volume of gas produced.
-measure the amount of gas collected over regular time intervals
Define enzyme
globular proteins that act as homogenous catalysts in living systems
What are enzymes used in
Rennin in the dairy industry
Yeast and amylase in the brewing industry
Lipase and protease in washing powders and detergent
What are the benefits of using enzymes as catalysts
Lower temperatures and pressure used
Operate in mild conditions and dont harm fabrics or foods
Biodegradable
Allow reactions to take place which form pure products with no side reactions removing the need for complex separation techniques
