Rate of Reaction

• The rate of reaction refers to how quickly the reactants in a chemical reaction are converted into products.
• It can be measured by the change in volume of gas produced, the change in mass (usually as mass is lost when a gas is formed), or the disappearance of a reactant over time.
• Factors that affect the rate of reaction include temperature, concentration (pressure for gases), surface area of solid reactants, the presence of a catalyst, and the nature of the reactants.
• Increasing the temperature increases the rate of reaction because particles have more energy and collide more often and with greater energy.
• Increasing the concentration of the reactants in solution, or the pressure for gases, leads to more frequent collisions between particles, hence increasing the rate of reaction.
• Increasing the surface area of solid reactants exposes more particles to the other reactants, resulting in a greater frequency of collisions and hence, a higher reaction rate.
• Catalysts increase the rate of a reaction by offering a different reaction pathway with a lower activation energy. They remain chemically unchanged at the end of the reaction.
• The nature of the reactants (e.g., what substances are reacting) can affect the frequency and energy of collisions, which in turn can influence the rate of reaction.
• The rate of reaction can be represented graphically, with the x-axis typically representing time and the y-axis representing concentration, volume of gas produced, or loss of mass.
• Reaction rate equations show the relationship between the rate of reaction and the concentrations of the reactants. The rate equation for a reaction between substances A and B could be in the form: rate = k[A]^m[B]^n .
• The collision theory states that reaction rates are directly proportional to the number of effective collisions between reactant molecules. It emphasises that particles must collide with sufficient energy (at least as much as activation energy) and correct orientation for a reaction to occur.
• Calculating the mean rate of reaction involves measuring the quantity of a reactant used or product formed over a period of time. It is usually expressed in terms of reactant used/product formed per unit time.
• The units of the rate of reaction can vary; they could be g/s, cm^3/s, mol/s etc., depending on what is being measured.
• In reversible reactions, the rate of the forward reaction decreases and the rate of the backward reaction increases until they become equal at equilibrium.