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Chapter 18

Chapter 18. Collision Theory. Atoms, ions, and molecules can react to form products when they collide with one another, if they have enough kinetic energy. Activation Energy Minimum energy that colliding particles must have in order to react. Complex

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Chapter 18

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  1. Chapter 18

  2. Collision Theory • Atoms, ions, and molecules can react to form products when they collide with one another, if they have enough kinetic energy. • Activation Energy • Minimum energy that colliding particles must have in order to react. • Complex • Unstable arrangement of atoms that forms momentarily at the peak of the activation-energy barrier. Also known as transition state. Activated

  3. The rate of a chemical reaction depends upon temperature, concentration, particle size, and the use of a catalyst. • Temperature • Increasing temp. speeds up reactions. • Concentration • Increasing concentration speeds up reactions. • Particle Size • Smaller particles have more surface area than larger ones. Increasing surface area speeds up reactions. • Catalysts • Increases the rate of a reaction without being used up during the reaction.

  4. Reversible Reaction The conversion of reactants to products and the conversion of products to reactants occur simultaneously. • Chemical Equilibrium • A state of balance when the rates of the forward and reverse reactions are equal.

  5. Le Châtelier’s Principle If a stress is applied to a system in dynamic equilibrium, the system changes in a way that relieves the stress.

  6. Factors Affecting Equilibrium • Changing the amount, or concentration, of any reactant or product in a system at equilibrium disturbs the equilibrium. • Increasing the temperature causes the equilibrium position of a reaction to shift in the direction that absorbs heat. • A change in the pressure on a system affects only gaseous equilibria that have an unequal number of moles of reactants and products.

  7. Equilibrium Constant is represented by (Keq). Solubility Product Constant is represented by (Ksp). Ksp=[C]c x [D]d Common Ion An ion that is found in both salts in a solution. Common Ion Effect The lowering of the solubility of an ionic compound as a result of the addition of a common ion.

  8. Free energy • Energy that is available to do work. • Spontaneous Reaction • Occurs naturally and favors the formation of products at the specified conditions. • Nonspontaneous Reaction • A reaction that does not favor the formation of products at the specified conditions. • Entropy(S) • A measure of the disorder of a system.

  9. Gibbs Free-Energy • ΔG = ΔH − TΔS • ΔG=Gibbs Free-Energy Change • ΔH=Change in Enthalpy • ΔS=Change in Entropy • T= Temperature(K) • If ΔG is negative then the reaction is spontaneous.

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