Chemical Reactions and Processes: A Concise Overview

Posted on Mar 24, 2025 in Chemistry

Chemical Equilibrium

The effect of a catalyst on a reaction mixture accelerates the reaction both directly and inversely. Equilibrium is reached more rapidly, but the catalyst does not change the amounts at equilibrium. Kc remains constant.

Factors affecting equilibrium (Le Chatelier’s principle):

  • If temperature increases, the equilibrium shifts towards the endothermic reaction.
  • If temperature decreases, the equilibrium shifts towards the exothermic reaction.

Acids and Bases

  1. Arrhenius theory does not include bases without OH, such as NH3.
  2. The ionic product of water is the product of the concentrations of H+ and OH–, at a fixed temperature.
  3. An amphoteric substance can act as both an acid and a base, depending on the medium.
  4. The stronger the bond of a binary acid (HI, HF), the weaker the acid.
  5. Common buffer solutions include a mixture of a weak acid or weak base and its salt. Buffers resist changes in pH upon the addition of small amounts of strong acid or base.

Solubility

  1. The solubility of NaCl decreases in the presence of AgCl.
  2. The solubility product is dimensionless.
  3. Only a saturated solution represents the maximum concentration of a salt that can be dissolved at a given temperature.
  4. The low solubility of hydroxides causes their solubility to increase as pH decreases.
  5. The stability constant in the formation of an ion complex is affected by the conditions of the solution when the complex forms.

Redox Reactions

  1. Reference potentials are used to build a stack with an electrode whose potential is to be measured.
  2. The Nernst equation is used to calculate the constant of a battery at equilibrium under standard conditions.
  3. In electrochemical reactions, the cell potential should have a positive value for the reaction to be spontaneous.
  4. Dry cell batteries are not electrochemical as they contain a fluid component.
  5. In electrochemical reactions, E (potential) is calculated by the Nernst equation.
  6. The equivalent weight of an agent depends on the redox reactions in which it participates.
  7. An oxidizing agent gains electrons (e–).
  8. Dichromate to chromium (III) gains 3e–.
  9. Observing the standard potentials: Ca+2/Ca = -2.8 V, Zn+2/Zn = -0.7 V, it can be concluded that Zn+2 is a better oxidant.

Kinetics

  1. Half-life is not always independent of the initial concentration of the reactant.
  2. According to Arrhenius, the rate constant is a function of the activation energy of the reaction.
  3. The order of a reaction is NOT always equal to the stoichiometric coefficients of the reactants in the balanced overall reaction.
  4. Integrated rate laws express concentration as a function of time, f(t).
  5. [k] = [M-1s-1]

Processes

  1. A steady state is when the concentration does not vary with time.
  2. Distillation is an operation based on the physical character of the material.
  3. Mass transfer processes are subject to monophasic conditions.
  4. Sedimentation is an operation basically controlled by the movement of solids by density.
  5. Packed columns are units for contact operations.
  6. Lyophilization is the industrial technique of water elimination by sublimation.
  7. Separation of one or more components of a liquid or gas mixture through a solvent is called liquid-liquid extraction.
  8. Reverse osmosis requires a semipermeable membrane.
  9. Flotation of particles is controlled by physical processes.
  10. Electrodialysis is a mass transfer process controlled by the substance.

Metallurgy

  1. Calcination allows the transformation of hydroxides into oxides.
  2. Purification includes: extraction, crushing, washing, leaching, precipitation, and drying.
  3. Electrochemical reduction is recommended for most electropositive metals.
  4. Distillation purifies metals only in the case of impurities more volatile than the metal.
  5. Zone refining is based on impurities being more soluble in the liquid phase than in the solid phase.
  6. In flotation, the ore is often part of the foam, while the gangue is suspended in water.
  7. Bronze is an alloy of Cu, Sn, and Zn.
  8. High limestone addition in the furnace transforms dross impurities into a floating state.
  9. Coke in blast furnaces is usually finely divided to facilitate its combustion.
  10. Basic additives of stainless steels are Cr and Mn.

Inorganic Industry

  1. The contact of SO3 in acid takes place in an absorption tower.
  2. Synthesis gas is decomposed into equimolar H2 and C.
  3. The synthesis of NH3 is a Haber-Bosch process, favored by high pressures and low temperatures.
  4. In the obtaining of Cu from chalcopyrite, the gangue is removed.
  5. Bauxite is fundamentally Al hydroxide.