Chapter 8: Chemical Kinetics
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What is reaction kinetics?
The study of the rates of chemical reactions.
What does the rate of a reaction measure?
How quickly the concentration of a reactant or product changes with time.
What does collision theory state about chemical reactions?
Particles must collide in the correct orientation and with sufficient energy to react.
What determines the average kinetic energy of particles?
The absolute temperature in Kelvin.
How does increasing temperature affect reaction rate?
It increases particle speed and the proportion of collisions with energy exceeding activation energy.
What is activation energy (Ea)?
The minimum energy required for particles to collide successfully.
What happens if particles do not have sufficient activation energy?
No reaction occurs.
What is the effect of concentration on reaction rate?
Higher concentration leads to more frequent collisions, increasing the reaction rate.
How does particle size affect the rate of reaction?
Smaller particles have greater surface area, increasing collision frequency and rate.
How does pressure affect reactions involving gases?
Higher pressure increases the rate by effectively increasing gas concentration.
What is the Boltzmann distribution?
It shows the distribution of particle energies at a given temperature.
How does the Boltzmann distribution change with temperature?
The curve flattens and shifts to the right as temperature increases.
What is a catalyst?
A substance that increases reaction rate by lowering activation energy and remains unchanged at the end.
How does a catalyst affect the Boltzmann distribution?
It increases the number of particles with energy greater than activation energy without changing the curve’s shape.
What is a homogeneous catalyst?
A catalyst in the same phase as the reactants.
What is a heterogeneous catalyst?
A catalyst in a different phase than the reactants.
Why does increasing temperature increase reaction rate?
Particles move faster, collide more often, and more particles exceed the activation energy.
How does a heterogeneous catalyst work?
It provides a surface for reactants to adsorb, increasing the probability of collisions.
What is the effect of enzymes on biochemical reactions?
They speed up reactions under mild conditions by lowering activation energy.
Why are enzymes more efficient than inorganic catalysts?
They increase reaction rates by factors of 10⁶ to 10¹² and work specifically without byproducts.
What are the optimal conditions for enzyme activity?
Around 35°C, pH 7, and atmospheric pressure.
How is activation energy visualized in an energy profile diagram?
As the peak energy barrier that must be overcome for reactants to form products.
How does temperature affect the proportion of successful collisions?
Higher temperatures increase the proportion of particles with energy greater than the activation energy.
What is the decomposition of hydrogen peroxide an example of?
A reaction catalyzed by a heterogeneous catalyst (MnO₂).