Law of conservation of Mass
During a chemical reaction, atoms are neither created nor destroyed, so the mass remains constant.
The rate at a particular point in time during the reaction = Slope of the Tangent to a curve
For a reaction to occur the particles must collide and the colliding particles must have enough activation energy to react
Reaction Profile Diagram
Diagram which shows how the energy content of a system changes during a reaction
Factors affecting Rates of Reaction
Nature of the reactants, Particle size (Surface area), Concentration, Temperature, Catalysts
Necessary conditions for dust explosion
A combustible dust, Ignition source, An oxidant, Dust suspended in the air at a high concentration, Dryness
Causes a small increase in number of collisions per unit time, and a large increase in the proportion of the collisions to have the required activation energy
Sodium thiosulfate and HCl
Reactants used in experiment to investigate the effect of concentration or temperature on reaction rate
Yellow precipitate of sulphur
Product used to monitor the progress of the reaction in experiment to investigate the effect of concentration or temperature on reaction rate
A substance that alters the rate of a chemical reaction but is not consumed in the reaction.
Properties of Catalysts
1. Chemically unchanged at the end of reaction but can be physically changed.
2. Usually specific.
3. Usually only need to be present in very small amounts.
4. In reversible reactions, both directions are catalysed equally (doesn't affect the position of equilibrium).
5. Can be destroyed by catalytic poisons.
Both reactants and catalyst are in the same phase (Iodine snake with KI + H2O2)
Intermediate Formation Theory
Occurs when one or more of the reactants combines with the catalyst to form an intermediate compound.
Surface Adsorption Theory
Occurs when reactant molecules settle on the surface of the catalyst forming temporary bonds between the molecules and the catalyst and causing an increase in concentration of the reactant molecules
Used in a car to convert toxins such as CO, NO, NO2 and hydrocarbons to harmless gases