Rates of Reaction

Rates of Reaction Overview

  • The rate of a chemical reaction refers to how quickly reactants turn into products.
  • Varying rates of reactions often underscore everyday phenomena, such as why food spoils or why fireworks explode.

Reactant Concentration

  • An increase in the concentration of reactants generally leads to an increase in reaction rate.
  • This happens because there are more particles present, increasing the chance of successful collisions between reactant particles.

Particle Size and Surface Area

  • The size of particles in a reaction and their surface area also influence the reaction rate.
  • Decreasing the size of particles (thus increasing surface area) speeds up reactions because it increases the chances of reactant particles colliding.

Reaction Temperature

  • The temperature of a reaction greatly affects the rate.
  • As temperature increases, particles move more quickly, which not only increases the likelihood of collisions but also ensures that more of these collisions result in a reaction.

Presence of Catalysts

  • Catalysts speed up chemical reactions without being used up in the process.
  • They provide an alternative reaction pathway with a lower activation energy, allowing more successful collisions and thus, a faster reaction.

Reaction Pressure

  • The pressure can also affect the rate of reactions, especially for gases.
  • Higher pressure compacts gas particles closer together, increasing the frequency of collisions and hence the rate of reaction.

Rate Equations and Graphs

  • Rate equations express the reaction rate as a function of concentrations of reactants.
  • Rate constants and orders of reaction can be determined by experiments, and represented graphically.
  • Half-life of a reactant is also a crucial concept pertaining to rates of reactions, especially in nuclear and biological systems.

Collision Theory

  • Collision theory explains rates of reaction on a molecular scale. For a reaction to occur, particles need to collide with the right orientation and sufficient energy.
  • The minimum energy particles need to react is called the activation energy.