Kinetics
Cards (6)
- Collision Theory:
- Chemical reactions occur when particles of substances collide
- Collisions must have energy greater than or equal to the activation energy of the reaction
- Particle orientation must be correct for a successful reaction
- Reaction Conditions:
- Impact the collisions of particles
- Conditions can be altered to provide particles with more energy
- Changing conditions can increase the likelihood of a collision occurring with sufficient energy to react and increase the rate of reaction
- Maxwell-Boltzmann Distribution:
- Not all molecules in a substance have the same amount of energy
- Energies are distributed in a pattern called the Maxwell-Boltzmann distribution
- Changing reaction conditions alters the shape of the curve, affecting the number of particles with energy greater than the activation energy
- The total area under the curve represents the total number of molecules in the sample, which must remain constant
- Effect of Temperature:
- Heating a substance transfers thermal energy, converted to kinetic energy
- Molecules move faster and further with increased temperature
- Increased movement leads to more frequent collisions with greater energy
- Increasing temperature increases the rate of reaction as more collisions of greater energy occur
- Effect of Concentration and Pressure:
- Increasing concentration leads to molecules being packed closer together, increasing the likelihood of collisions with greater energy
- Increasing pressure has a similar effect by packing molecules closer together in a smaller volume
- Both concentration and pressure increase the rate of reaction
- Effect of Catalysts:
- Catalysts increase the rate of reaction without being used up
- Provide an alternative reaction path with a lower activation energy
- The Maxwell-Boltzmann distribution curve remains unchanged in shape, but the position of the activation energy is shifted to the left, allowing a greater proportion of molecules to have sufficient energy to react