2.2 Rates of reaction Flashcards
define activation energy (part 1)
the minimum amount of energy that particles must have in order to start a reaction by breaking chemical bonds
how do catalysts allow a reaction to take place
via an alternative pathway
- lower activation energy
why can catalysts be reused
- not used up in a reaction
- not permanently changed
how do catalysts provide an economic and environmental benefit
they lower the activation energy, therefore reducing the amount of energy needed via burning fossil fuels. This reduces cost.
reduces carbon dioxide + greenhouse gas emissions, more sustainable
why can catalysts be negative for the environment
some are toxic
how do you calculate rate of reaction
rate = (change in conc)/(time)
name the 5 factors which affect the rate of reaction
- concentration(pressure for gases)
- temperature
- particle size
- catalyst
- light
why does increasing concentration affect rate
because there are more particles per unit volume which causes collisions to be more frequent which increases the rate of successful collision every second per unit volume
what is a heterogeneous catalyst
catalyst has a different physical state to the reactants
what is a homogeneous catalyst
catalyst has the same physical state to the reactants
how do heterogeneous catalysts work?
ADSORPTION
-The reactant molecules form weak bonds with catalyst surface
what are the 3 stages of heterogeneous catalysts
- adsorption
- Reaction
- desorption
how do heterogeneous catalysts work?
REACTION
reaction takes place to form products
how do heterogeneous catalysts work?
DESORPTION
product molecules are released from surface of the catalyst
