Rates Of Reaction Flashcards
Rate of reaction
Change in concentration of a reactant(or product) per unit time
Average rate
The amount of product/ period of time
Activation energy
Minimum energy colliding particles must have in order to react
Catalyst
A substance that alters the rate of a chemical reaction but is not used up at the end of the reaction
Factors affecting rate of reaction
- Temperature
- Concentration
- particle size
- nature of reactants
Temperatures affect on reaction rate
Th higher the Temperature the larger the proportion of particles that have activation energy
Particle size affect on reaction rate
The smaller the particles- the faster the rate of reaction due to larger surface area.
Nature of reactants
Ionic compounds react very quickly/ covalent compounds react slowly
Auto catalyst
One of the products of the reaction catalyses the reaction
Why does the rate of chemical reaction generally decrease with time?
Concentration decreases and reactants are used up
Give three conditions necessary for a dust explosion to occur
Dryness
Above certain concentration
Enclosed space
Effective Collision
Reaches activation energy and results in product formation
Homogenous catalyst
Catalyst and reactants are in Same phase
Heterogeneous catalysts
Catalyst and reactants in different phases
Surface absorption
Reactants are absorbed onto the surface of the catalyst and the products released when formed thus freeing active site again
Intermediate compound formation
Catalyst forms unstable intermediate with reactants and decomposes readily releasing the products
Explain how the type of bonding in the reactants influences the rate of a chemical reaction in aqueous solutions
Ionic compounds react quickly in solution as dissociated ions only need to collide
How could you reduce the rate of reaction that takes place in solution?
Lowering the temperature or lowering the concentration
two observations of the oxidation of methanol using platinum wire
Wire glows/ odour of methanol
Absorption
The attachment of liquid or gaseous molecules to a solid surface
Explain how absorption affects the rate of oxidation
Bonds weekend and lower activation energy/ more effective collisions
Explain how a catalyst poison like sulfur interferes with a catalyst
Active site occupied/blocked by poison
How does temperature speed up reaction?
The higher the temperature the larger the proportion of particles that have activation energy.
How does concentration speed up a rate of a reaction?
Closer molecules means more collisions per unit time
How does a catalyst speed up a rate of reaction?
Lowers activation energy/more effective collisions / forms activated complex
Name two of the metals used as catalysts in catalytic converters
Platinum
Rhodium
Name a substance that could poison the catalysts of the catalytic converter.
Sulfur compounds/ lead compounds
Two products in oxidation of methanol using platinum wire as a catalyst
Methanol and hydrogen gas
Heat of reaction formula
Heat/no. Of moles
