Reaction Conditions

• The conditions of a reaction impact the collisions of the particles and can be altered to give the particles more energy. The conditions can be changed to increase the likelihood of a collision occurring with sufficient energy to react, leading to a greater rate of reaction.
• On a concentration-time graph, the rate of reaction is equal to the gradient of a curve at a given point. By drawing a tangent to a curve at this point, you can calculate the rate of reaction. To find the initial reaction rate, draw a tangent to the curve at the point where the time is zero.
• Rate of reaction = 1/time taken
• When a substance is heated, thermal energy is transferred to it and converted into kinetic energy, so the particles move faster in a random motion. This means that collisions occur more often and with greater energy. Therefore, more collisions are successful (have energy exceeding the activation energy), increasing the rate of reaction.
• When temperature increases, the Maxwell-Boltzmann distribution will shift to the right, since a greater proportion of molecules have energy greater than or equal to the activation energy.
• When the concentration of a sample is increased, there are more molecules of substance in the same volume, so are packed closer together. Therefore, collisions between molecules become more likely and the probability of a collision occurring with sufficient energy increases. Therefore, the rate of reaction increases.
• Increasing the pressure of a gas has a similar effect a molecules are packed closer together into a smaller volume.
• Even though increasing concentration/pressure makes successful collisions occur more frequently, the energy of the individual particles doesn't change. Therefore, the shape of the Maxwell-Boltzmann distribution doesn't shift.
• Increasing the surface area of a reactant (e.g. by crushing it into powder) increases the number of exposed reactant particles. Therefore, there are more frequent, successful collisions, so the rate of reaction increases.
• Similar to concentration/pressure changes, altering the surface area doesn't change the energy of the individual particles. Therefore, the Maxwell-Boltzmann distribution doesn't change.