U3 controlling the rate Flashcards
State the formula for rate of reaction
Change in mass/ change in time
State the formula for relative rate of reaction
1/t (t = time)
describe collision theory
particles must collide to react;
not all collisions are successful;
particles must collide with enough energy;
collision geometry must be correct.
Explain why reaction rates must be controlled in industrial processes
If the rate is too low then the process will not be economically viable; if it is too high there will be a risk of explosion
state four factors which affect rate of reaction
concentration, pressure, particle size, temperature
explain how an increase in temperature increases rate of reaction
more particles now have energy in excess of activation energy
explain how a decrease in particle size increases rate of reaction
smaller particle size of reactants provides a greater surface area that collisions can take place on.
what is enthalpy change
energy difference between the products and the reactants
what is the activated complex and where is it found on a potential energy diagram
an unstable arrangement of electrons which is very high in energy - found at peak of PED
describe catalysts and their role
speed up chemical reactions without being used up. they work by forming temporary bonds with reactants causing bonds within reactants to weaken. catalysts provide an alternative reaction pathway with a lower activation energy
what is temperature
a measure of the average kinetic energy of the particles in a substance
what is activation energy
the minimum kinetic energy required by colliding particles before a reaction may occur
