particles in the solid state, however, are not free to move, so only the particles at the surface of the solid are able to collide with other particles; this reduces the collision frequency and reduces the rate of reaction the rate of reaction in solids can be increased by reducing the particle size, and hence increasing the surface area exposed to collisions: A large particle size, fewer of the blue solid particles can collide with the red particles, slower reaction – B small particle size, more of the blue solid particles can collide with the red particles, faster reaction – Factors affecting rate of reaction summary – Effect: On collision On collision On activation On fraction of On rate frequency energy energy successful collisions Increase Increases No effect No effect No effect Increases concentration (liquids and gases) Increase pressure Increases No effect No effect No effect Increases (gases) Increase Increases Increases No effect Increases Increases temperature Add a catalyst No effect No effect Decreases Increases Increases Lesson 4 Orders of Reaction and Rate Equations – Introducing Rate Equations The relationship between the rate of a chemical reaction and the concentration of the reactants is by the rate equation of the reaction Consider the reaction A + 3B 2C + 4D The rate of this chemical reaction is given by the equation: rate = k[A]x[B]y [A] is the concentration of A, and [B] is the concentration of B. x and y are the orders of reaction with respect to A and B respectively. The order of reaction with respect to a given reactant is the power of that reactant's concentration in the rate equation. The sum of powers, in this case x + y, is known as the overall order of reaction: The overall order of reaction is the sum of the powers of the reactant concentrations in the rate equation k is the rate constant of the reaction. The rate constant is the constant of proportionality in the rate equation Determining orders of reaction from initial rate measurements
particles in the solid state, however, are not free to move, so only the particles at the surface of the solid are able to collide with other particles; this reduces the collision frequency and reduces the rate of reaction the rate of reaction in solids can be increased by reducing the particle size, and hence increasing the surface area exposed to collisions: A – large particle size, fewer of the blue solid particles can collide with the red particles, slower reaction B – small particle size, more of the blue solid particles can collide with the red particles, faster reaction Factors affecting rate of reaction – summary Effect: On collision frequency On collision energy On activation energy On fraction of successful collisions On rate Increase concentration (liquids and gases) Increases No effect No effect No effect Increases Increase pressure (gases) Increases No effect No effect No effect Increases Increase temperature Increases Increases No effect Increases Increases Add a catalyst No effect No effect Decreases Increases Increases Lesson 4 – Orders of Reaction and Rate Equations Introducing Rate Equations The relationship between the rate of a chemical reaction and the concentration of the reactants is by the rate equation of the reaction Consider the reaction A + 3B 2C + 4D The rate of this chemical reaction is given by the equation: rate = k[A]x[B]y [A] is the concentration of A, and [B] is the concentration of B. x and y are the orders of reaction with respect to A and B respectively. The order of reaction with respect to a given reactant is the power of that reactant's concentration in the rate equation. The sum of powers, in this case x + y, is known as the overall order of reaction: The overall order of reaction is the sum of the powers of the reactant concentrations in the rate equation k is the rate constant of the reaction. The rate constant is the constant of proportionality in the rate equation Determining orders of reaction from initial rate measurements
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