Kinetics Flashcards

Interactive active recall cards for collision theory, Maxwell-Boltzmann distributions, factors affecting rate, and catalysts.

Collision Theory: read all 4 questions and answers

State collision theory.
For a reaction to occur, particles must collide with the correct orientation and with energy greater than or equal to the activation energy.
Define activation energy (Ea).
The minimum energy required by colliding particles to start a reaction by breaking bonds.
Define rate of reaction.
The change in concentration of a reactant or product per unit time (units: mol dm^-3 s^-1).
Why do most collisions not lead to a chemical reaction?
Because colliding particles often lack the minimum required activation energy, or do not collide in the correct orientation.

Maxwell-Boltzmann Distribution: read all 5 questions and answers

What does the area under a Maxwell-Boltzmann distribution curve represent?
The total number of gaseous molecules in the sample.
Why does the Maxwell-Boltzmann curve start at the origin?
Because no molecules in the sample have zero energy.
Explain what the peak of a Maxwell-Boltzmann curve represents.
The most probable energy of the molecules in the sample.
How does the Maxwell-Boltzmann distribution curve change as temperature increases?
The peak shifts to the right and down (becomes flattened), and the fraction of molecules with energy greater than Ea increases significantly.
Why does a small increase in temperature cause a large increase in reaction rate?
It significantly increases the fraction of molecules with energy greater than or equal to the activation energy, leading to a much higher frequency of successful collisions.

Factors Affecting Rate: read all 4 questions and answers

Explain how increasing the concentration of a solution increases the rate of reaction.
It increases the number of reacting particles per unit volume, which increases the frequency of collisions.
Explain how increasing the pressure of a gas increases the rate of reaction.
Gas molecules are pushed closer together, increasing the number of particles per unit volume and therefore increasing the frequency of collisions.
Explain how increasing the surface area of a solid reactant increases the rate of reaction.
More particles are exposed at the surface, allowing more collisions to occur per unit time, which increases the frequency of collisions.
Explain how increasing the temperature increases the rate of reaction.
Particles gain kinetic energy and move faster, increasing collision frequency. Most importantly, a much larger fraction of particles have energy greater than or equal to the activation energy.

Catalysts: read all 5 questions and answers

Define catalyst.
A substance that increases the rate of a chemical reaction without being used up in the process.
How does a catalyst increase the rate of reaction?
It provides an alternative reaction pathway with a lower activation energy.
Describe the effect of a catalyst on a Maxwell-Boltzmann distribution curve.
The activation energy (Ea) shifts to the left, so a larger fraction of molecules now have energy greater than or equal to the new activation energy.
Distinguish between homogeneous and heterogeneous catalysts.
A homogeneous catalyst is in the same physical state as the reactants, whereas a heterogeneous catalyst is in a different physical state.
Why are catalysts widely used in industrial chemical processes?
They allow reactions to occur at lower temperatures and pressures, saving energy costs and reducing carbon emissions.