3.2.2 Reaction Rates Flashcards
Effect of concentration on the rate of reaction
- as conc increases there are more particles per unit volume
- more collisions per second resulting in more reactions per second
- increase in the rate of reaction
Effect of gas pressure on rate of reaction
- as pressure increases there are more particles per unit volume
- more collisions per second resulting in more reactions per second
-increase in rate of reaction
Effect of particle size on rate of reaction
- small particles have a larger surface area
- more collisions per second
- more collisions resulting a reaction
- rate of reaction increases
Effect of temperature on rate of reaction
- particles have greater kinetic energy
- more collisions per second
- more collisions result in reactions
- more particles will have more energy than the activation energy
What is the definition of rate of reaction?
Rate = change in concentration / time
moldm-3s-1
What conditions must be satisfied for a chemical reaction to occur by collisions?
- must collide
- with sufficient kinetic energy
- in the correct orientation
- must have equal to or over the activation energy
What is the activation energy?
The minimum amount of energy required for a chemical reaction to occur
What is the role of a catalyst?
- increases reaction rate without being used up in the overall reaction
- allows a reaction to proceed on an alternative pathway with lower activation energy
- (therefore more particles have greater than the activation energy)
What are heterogeneous catalysts?
- catalysts that are in a different phase as the reactants
- e.g. solid catalyst in liquid reaction
- e.g. solid iron in the Haber process to make gaseous ammonia
- nitrogen + hydrogen -> ammonia
Why are catalysts important?
- great economic importance and benefits for increased sustainability
- by lowering temperatures and reducing energy demand from combustion of fossil fuels with resulting decrease in CO2 emissions
What is a homogeneous catalyst?
- catalysts that are in the same phase as the reactants
- e.g liquid catalyst in a liquid reaction
- e.g. concentrated sulphuric acid added to an esterification reaction
- e.g. enzymes in body
What is the Boltzmann distribution curve?
- shows how the energies of the particles are distributed in the sample or substance being used
What are the rules of the Boltzmann distribution curve?
- no particles have no energy and no particles have the maximum amount of energy
- the curve never touches the axis (within 1/2 square of axis)a
What is does the area under the Boltzmann distribution curve show?
- total area under the curve = total number of particles in sample
- area under graph greater than Ea = number of particles that can react - successful collisions per second
Draw the Boltzmann distribution curve
See notes
Draw the Boltzmann distribution curve with a catalyst (lower Ea)
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More particles with energy greater than or equal to Ea, so more successful collisions per second
Draw the Boltzmann distribution curve for lower, medium and higher temperature
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