Chemistry Module 5

• Le Chatelier's principle states that when a system at equilibrium is subjected to a change in temperature, pressure, or concentration, the system will shift in a way that counteracts the change.
• The equilibrium constant relates the concentration of products to the concentration of reactants in a reversible chemical reaction at equilibrium.
• The solubility product constant (Ksp) is used to determine whether an ionic compound will dissolve in water based on its Ksp value.
• The equilibrium concentration of reactants and products remains constant.
• Acid-base reactions involve proton transfer between acids and bases.
• Aqueous solutions can be classified as acidic, basic, or neutral depending on their pH values.
• A catalyst increases the rate of a reaction without being consumed by it.
• Enzymes are biological catalysts that lower activation energy barriers for reactions.
• Increasing temperature can increase the rate of an enzyme-catalyzed reaction up to a certain point called the optimum temperature.
• A buffer solution can resist changes in pH due to the addition of small amounts of acid or base because it contains both a weak acid and its conjugate base or a weak base and its conjugate acid.
• A change in one variable affects the position of equilibrium but not the overall amount of substance present.
• Bronsted-Lowry acid-base theory defines acids as substances that donate hydrogen ions (H+), while bases accept H+ ions.
• Increasing the concentration of reactant(s) shifts the equilibrium towards the formation of more product(s).
• Acid-base indicators are substances that undergo color changes as they move from one form to another in response to changing pH values.
• Strong acids completely dissociate into H+ ions in solution, while weak acids only partially dissociate.
• pH is defined as -log[H+] and measures the hydrogen ion activity in aqueous solutions.
• Lewis acid-base theory describes acids as electron pair acceptors and bases as electron pair donors.
• Enzymes are biological catalysts that lower activation energy barriers for specific biochemical reactions.
• Bases are substances that accept hydrogen ions from other compounds.
• Decreasing the concentration of product(s) shifts the equilibrium towards the formation of more product(s).
• Weak bases have low concentrations of OH- ions in solution.
• Increasing temperature generally increases the rate of chemical reactions due to increased kinetic energy of particles.
• Strong acids completely dissociate into their constituent ions in solution, while weak acids only partially dissociate.
• Changing pH can affect the activity of enzymes, with optimal conditions varying from one enzyme to another.
• The Le Chatelier's principle states that when a system at equilibrium is subjected to stress (change), the system will respond so as to minimize the effect of the stress.
• Lewis acid-base theory states that Lewis acids are electron pair acceptors, while Lewis bases are electron pair donors.
• The Bronsted-Lowry definition of an acid is a proton donor, while the Arrhenius definition is a compound that releases H+ ions when dissolved in water.
• Buffer capacity is the amount of strong acid or base required to change the pH of a given volume of buffer solution by one unit.
• Le Chatelier's principle


  This is used to predict the changes that will occur following a change in the conditions (that is, concentration of chemicals, pressure, volume or temperature of a system).
• Le Chatelier's principle: to predict the outcome of a change in conditions.


  1 What change is imposed?

  2 What is the opposite of the change? (This is what the system will do.).

  3 Which reaction direction is favoured - the forward or reverse?

  4 Does equilibrium shift to the left or right?

  5 What happens to the concentrations of each aqueous substance or gas?
• forward reaction


  Reactants form products
• reverse reaction


  Products form reactants
• static equilibrium


  Reactions occurring in one direction, reactants produce products until one reactant runs out and the reaction stops.
• dynamic equilibrium


  a state of balance between continuing reactions. E.g. products to reactants to products to reactants
• physical change


  The products do not include any new substances.
• chemical change


  The reactants produce new substances.
• activation energy


  Amount of energy required to break the bonds of the reactants.
• chemical system


  The chemicals involved in a reaction
• closed system


  All the chemicals within the reaction are contained within a certain space.
• collision theory


  For a reaction to occur, the particles must collide with sufficient energy to break the bonds and have the appropriate orientation to allow the new bonds to form.