Kinetics 5 Flashcards
collision theory
for a reaction to take place between two particles, they must collide with enough energy to break bonds
factors that affect the rate of a chemical reaction
increasing the temperature
increases the speed of the molecules which in turn increases the energy and number of collisions
factors that affect the rate of a chemical reaction
increasing the concentration of a solution
more particles are present in a given volume then collisions are more likely and the reaction rate would be faster. however, as a reaction proceeds, the reactants are used up and their concentration falls. so, in most reactions, the rate of reaction drops as the collisions are more likely
factors that affect the rate of a chemical reaction
increasing the pressure of a gas reaction
there are more molecules or atoms in a given volume so collisions are more likely
factors that affect the rate of a chemical reaction
increasing the surface area of solid reactants
greater the total surface area, more of the particles are available to collide with molecules in a gas or liquid
factors that affect the rate of a chemical reaction
using a catalyst
a catalyst is a substance that can change the rate of chemical reaction without being chemically changed itself
maxwell-Boltzmann distribution
- no particles has zero energy
- most particles have intermediate energies
- a few have very high energies
activation energy
reaction to take place, a collision between particles must have enough energy to start breaking bonds.
the area under the line represents the number of particles with enough energy to react.
effect of temperature on the rate of reaction
at high temperature, the peak of the curve is lower and moves to the right. the number of particles with very high energy increases.
catalysts
provide a different pathway for the reaction, one with a lower activation energy
Don’t get used up in the reaction
(A catalyst is a substance that increases the rate of a chemical reaction without being changed in chemical composition or amount)
what catalyst does the Haber process use ( and uses)
- iron
- making fertilisers
catalyst and uses of
4NH3 + 5O2 — 4NO +6H20 (nitric acid)
- platinum and nickel
- making fertilisers and explosives
catalyst and uses of
hydrogenation
- nickel
- margarine
catalyst and uses of cracking hydrocarbon chains from crude oil
- aluminium oxide and silicon dioxide zeolite
- making petrol
catalyst and uses of the catalytic converter reactions in car exhausts
- platinum and rhodium
- removing polluting gases
catalyst and uses of hydration of ethene to produce ethanol
- H+ absorbed on solid silica, phosphoric acid (H3PO3)
- making ethanol;
catalyst and uses of esterification
- H+
- Making solvents
catalytic converter
- reduce levels of a number of polluting gases.
- honeycomb made of ceramic material coated with platinum and rhodium metals
carbon monoxide + nitrogen oxides — nitrogen + carbon doixide
hydrocarbon + nitrogen oxide — nitrogen + carbon dioxde + water
Zeolites
Mineral
Open pore structure
48 are naturally formed
Used in petrochemical industry
Hardening
Unsaturated fat (margarines)
Hydrogen added
Nickel catalyst
Nickel filtered off at the end
Catalyst and ozone layers
CFC were used (in sovalent / aerosol propellants)
Unreactive until UV
(Nitrogen monoxide acts a catalyst)
Rate of reaction
Amount of reactants used / time
Reaction rate, the speed at which a chemical reaction proceeds
Dynamic reaction
Closed system
Constant temperture
Le chateliers principle
If a reaction at equilibrium is subjected to a change in concentration,pressure or temperature, the position of equilibrium will move to counteract the change
N2O4 ↔️ 2NO2. +57.2kjmol-1
NO2 brown
N2O4 colourless
If you change the pressure then the colour changes because it would prefer on side
Ethanol
C2H4 + H2O ↔️ C2H5OH
-46Kjmol-1
60-70 atmospheres
300 degrees
Phosphoric acid catalyst
To save money / materials - un reactive ethene is separated and recycled back into the reactor
Methanol
2H2 + CO ↔️ CH3OH
50-100 atmospheres
250 degrees
Copper / zinc oxide / aluminium oxide
Change in concentration
More reactant = more product
More product = more reactants
Change in pressure
Only affects gases
Increase in pressure = favours the side with less moles
Change in temperture
Increase temperature (add heat) Shifts in the endothermic direction to a absorb the heat
Decrease temperature (remove heat) Shifts to the exothermic to replace the heat
why do most collisions do not lead to a reaction ?
do not have appropriate orientation to one another in the collision to lead to a reaction. Reactants must have enough energy to overcome the activation energy barrier in order to become products.
