GENERAL CHEMISTRY ?

• Collision theory states

  that the rate of a chemical reaction is proportional to the number of collisions between reactant molecules
• activation energy

  Collisions must be sufficiently energetic (kinetic energy) to break chemical bonds; such energy is identified
• Effective Collisions

  are those that result in a chemical reaction and a new product was formed.
• A collision

  is considered ineffective when one doesn’t lead to product formation
• Ineffective collision

  Occurs when molecules strike with a different orientation and then they just bounce off each other without reacting.
• CATALYSTS

  are substances that help speed up the rate of chemical reactions

  They are not changed or consumed during the reaction but instead they provide a new mechanism for a new reaction to occur
• CATALYSIS

  is the process of speeding up a reaction by using a catalyst
• solid catalysts

  can be a metallic element such as metals, oxides, sulfides or halides or a semi-metallic element like boron, aluminum and silicon.
• Gaseous and liquid catalysts

  usually used in their pure form or in combination with suitable carriers or solvents while solid catalysts are commonly dispersed in other substances known as catalyst supports.
• HOMOGENEOUS CATALYSIS

  When a catalyst and the reactants are in the same physical state or phase, the reaction is considered homogeneously catalyzed. This happens mostly with gaseous catalyst-reactant pairs.
• HETEROGENEOUS CATALYSIS

  When the catalyst and the reactant are in different phases, the reaction is said to be heterogeneously catalyzed. Common heterogeneous catalyst mostly include inorganic or a non-carbon-containing solid like elemental metals, sulfides and metallic salts.
• Enzymes

  are proteins that function as catalyst in all living systems They are natural catalysts found in the body. They are responsible for many essential biochemical reactions. They play a role in everything from copying genetic material to its important role in digestion and more.
• Entropy

  is simply a measure of how much the energy of the particles become more spread out in a process

  It is also defined as the thermodynamic quantity that expresses the degree of disorder in a system. If the system becomes less ordered, the entropy increases.
• Number of Possible Microstates

  The greater the number of possible microstates for a system, the higher the entropy. Microstate refers to the arrangement of the energy of each molecule in the whole system at one instant.
• Phases

  Different phases have different entropies. Gases have higher entropy than liquids and liquids have higher entropy than solids. The particles of gases are more random than liquids and solids because they move freely in the bigger spaces between them.
• Temperature

  The higher the temperature, the higher is the entropy.
• Mixture vs Pure Solvent

  Compared to a pure substance, in which all particles are identical, the entropy of a mixture of two or more different particle types is greater.
• Dissolved Substances vs. Precipitate When a solid dissolve in a liquid such as sodium chloride in water the particles of the solid experience both a greater freedom of motion and additional interactions with the solvent particles
• Presence of a Gas

  The side of the equation with more moles of gas has a higher total entropy. This is because a greater number of moles indicates a greater number of gas particles and a greater number of arrangements of the gas particles.
• CALCULATING ENTROPY

  ΔS∘rxn = Σ S∘(products)−Σ S∘(reactants)
• spontaneous process

  is one that occurs without outside intervention

  It states that a spontaneous process will increase the entropy of the universe
• Reaction

  will never spontaneously move away from equilibrium and will always move spontaneously towards equilibrium.
• Entropy change measures the dispersal of energy

  how much energy is spread out in a particular process, or how widely spread out it becomes (at a specific temperature)
• non spontaneous

  If a reaction does not occur under specified conditions
• Reaction is at equilibrium state

  if the rate of the forward reaction equals the rate of the backward reaction
• dynamic equilibrium

  Equilibrium is denoted in a chemical equation by the ⇌ symbol

  A two-headed arrow signifies that a reaction can proceed on a forward or on a reverse direction
• Dynamic equillibrium


  The double arrow implies that the reaction is going in both directions. Such reactions are called reversible reactions.
• Le Chatelier’s Principle

  Is a rule which helps to predict the direction in which the equilibrium reaction will go through when a change in concentration, pressure, volume, or temperature occurs
• Le Chatelier’s principle

  adding additional reactant to a system will shift the equilibrium to the right, towards the side of the products.
• Changes in pressure

  do not affect the concentrations of reacting species in condensed phases (in aqueous solution) because solids and liquids are virtually incompressible. On the other hand, concentrations of gases are greatly affected by changes in pressure.
• change in concentration

  pressure or volume alters the position of the equilibrium but not the magnitude (value) of the equilibrium constant
• function of a catalyst

  Is to speed up the reaction by lowering the activation energy. The catalyst lowers the activation energy of the forward reaction and reverse reaction to the same extent.
• Brønsted-Lowry theory

  Describes acid-base interactions in terms of proton transfer between chemical species
• Bronsted acid

  Is a substance capable of donating a proton (H+ ions)
• Bronsted base

  Is a substance capable of accepting a proton (H+ ions)
• conjugate acid-base pair

  Which can be defined as an acid and its conjugate base or a base and its conjugate acid
• Acid-Base Properties of Water

  Water is a special molecule and has many unique properties that make it essential for all life on Earth
• pH of a solution

  which stand for “power of hydrogen” is defined as the negative logarithm of the hydrogen ion concentration
• Molar (M) or mol/L

  And as such the measure of acidity and basicity of a solution
• pH of an aqueous solution

  pH= -log [H3O+] or pH= -log [H+]