Kinetics

• When will a reaction take place?

  When the particles collide
• What is activation energy?

  Activation energy is the minimum amount of energy required for a chemical reaction to occur.
• How must reacting particles collide?

  With the correct orientation
• What is the rate of reaction?

  The change in concentration (of reactant/product) per second.
• How do you calculate the reaction rate?

  $\frac{change\ in\ concentration\ \left(mol\ dm^{-3}\right)}{time\ \left(s\right)}$
• What effect does concentration have on the rate of a reaction?

  This increases the number of particles in a given volume, leading o more frequent collisions, the rate of reaction increases
• What effect does pressure have on the rate of a reaction?

  This forces the particles closer together, increasing the frequency of collisions, the rate of reaction increases
• What effect does temperature have on the rate of a reaction?

  Provides particles with more kinetic energy, causing hem to move faster. More particles collide with energy greater than/ equal to activation energy, increasing the number of successful collisions and speeding up the reaction
• What effect does the surface area of solid reactants have on the rate of a reaction?

  Exposes more particles to collisions, rate of reaction increases
• What effect does the presence of a catalyst have on the rate of a reaction?


  A catalyst provides an alternative reaction pathway with a lower activation energy, a greater proportion of particles have sufficient energy to react, more successful collisions and an increased rate of reaction
• What is a Maxwell-Boltzmann distribution?

  The distribution of molecular energies in a gas at a given temperature, providing graphical representation of how many gas molecules have various amounts of inertia ergy
• What does the area under the curve of a Maxwell-Boltzmann distribution show?

  The total number of molecules
• What does the peak on the Maxwell-Boltzmann distribution represent?

  The most probable energy, where most molecules have this amount of energy
• Why does the Maxwell-Boltzmann distribution always begin at the origin?


  All particles have energy, there can be no particles which have no energy
• What happens to the Maxwell-Boltzmann curve at higher temperatures?

  The curve shifts to the right and flattens, as average kinetic energy of the molecules increases. More molecules have energies above the activation energy leading to a higher rate of successful collisions so a faster reaction rate. The peak of the curve is lower and occurs at a higher energy
• What happens t the Maxwell-Boltzmann curve at low temps?

  The curve shifts to the left and becomes taller, more molecules have lower kinetic energy. fewer molecules have enough energy to surpass the activation energy, reaction rate is slower. peak of curve is higher and occurs at a lower energy
• What effect des a catalyst have on the Maxwell-Boltzmann distribution?

  It doesn’t change the shape but it does lower the activation energy so a greater proportion of molecules now have enough energy to surpass the activation energy, so the rate of reaction increases as more molecules can successfully collide and react