AS

Chapter 4 - Reactions in Aqueous Solutions

4.1 General Properties of Aqueous Solutions

  • A solution is a mixture of two or more components that is homogenous.
    • The solute is the substance that is present in lesser quantities.
    • The solvent is the material that is present in greater quantities.
    • Aqueous solutions are those in which the solute is a liquid or solid at first, and the solvent is water.
  • There are two types of solutes that dissolve in water: electrolytes and nonelectrolytes.
    • An electrolyte is a material that, when dissolved in water, produces an electrically conductive solution.
    • When dissolved in water, a nonelectrolyte does not conduct electricity.

4.2 Precipitation Reactions

  • The precipitation reaction, which results in the creation of an insoluble product known as a precipitate, is a typical type of reaction that happens in an aqueous solution.
    • A precipitate is a solid that separates from a solution because it is insoluble.
    • Ionic chemicals are used in most precipitation reactions.
  • A metathesis reaction is a reaction in which portions of two substances are exchanged.
  • It is determined by the solute's solubility, which is defined as the greatest amount of solute that may dissolve in a given amount of solvent at a particular temperature.

4.3 Acid-Base Reactions

  • The definitions of acids and bases given by Arrhenius are limited in that they only apply to aqueous solutions.
    • A proton donor is a Bronsted acid.
    • A proton acceptor is a Bronsted base.
    • The hydronium ion is the hydrated proton, H3O+(aq).
  • The reaction in which a Brnsted acid (HCl) contributes a proton to a Brnsted base is depicted in this equation (H2O).
  • Hydrochloric acid (HCl), nitric acid (HNO3), acetic acid (CH3COOH), sulfuric acid (H2SO4), and phosphoric acid are some of the most regularly utilized acids in laboratories (H3PO4).
    • The first three are monoprotic acids, which means that when ionized, each unit of the acid generates one hydrogen ion.
  • Because each unit of sulfuric acid (H2SO4) releases two H+ ions, it is a diprotic acid.
  • Tricrotic acids, which produce three hydrogen ions, are uncommon.
    • Phosphoric acid is the most well-known tricrotic acid.

4.4 Oxidation-Reduction Reactions

  • While acid-base reactions are proton-transfer events, oxidation-reduction reactions, or redox reactions, are electron-transfer reactions.
  • A half-reaction that illustrates the electrons involved in a redox reaction in detail.
    • The half-reaction that involves the loss of electrons is referred to as an oxidation reaction.
    • A reduction reaction is a half-reaction in which electrons are gained.
    • Magnesium is oxidized during the production of magnesium oxide. It's called a reducing agent because it transfers electrons to oxygen, causing it to be reduced.
    • Because it receives electrons from magnesium, oxygen is reduced and functions as an oxidizing agent, causing magnesium to be oxidized.
  • It's helpful to give oxidation numbers to the reactants and products to keep track of electrons in redox processes.
  • The oxidation number, commonly known as the oxidation state, of an atom, indicates how many charges it would have in a molecule if electrons were transported.
  • Combination, decomposition, combustion, and displacement reactions are some of the most prevalent oxidation-reduction reactions.
    • A combination reaction occurs when two or more chemicals react to produce a single result.
    • The reaction of decomposition is the polar opposite of the reaction of combination.
    • A decomposition reaction occurs when a chemical is broken down into two or more components.
    • A combustion reaction occurs when a chemical combines with oxygen, usually releasing heat and light in the form of a flame.
    • An ion of a compound is replaced by an ion of another element in a displacement reaction
  • In a disproportionation process, an element in one oxidation state gets oxidized and reduced at the same time.

4.5 Concentration of Solutions

  • The amount of solute present in a given amount of solvent, or a given amount of solution, is referred to as the concentration of a solution.
  • Molarity (M), also known as molar concentration, is the number of moles of solute per liter of solution and is one of the most often used units in chemistry.
    • Where n is the number of moles of solute and V denotes the volume of the solution in liters, molarity is defined.

4.6 Gravimetric Analysis

  • Gravimetric analysis is a technique for analyzing data based on mass measurements.
  • First, an unknown-composition sample ingredient is dissolved in water and allowed to react with another component to generate a precipitate.
    • The precipitate is filtered, dried, and weighed after that.
  • We can compute the mass of a specific chemical composition of the original sample using the mass and chemical formula of the precipitate created.
  • Finally, we may calculate the percent composition by mass of the component in the original compound using the mass of the component and the mass of the original sample.

4.7 Acid-Base Titrations

  • Titration is the most convenient method for conducting quantitative research of acid-base neutralization processes.
    • In a titration, a solution with an exact concentration, known as a standard solution, is gradually added to another solution with an unknown concentration until the chemical reaction between the two solutions is complete.
  • A sudden change in the color of an indicator in the acid solution usually indicates the equivalence point.
    • The point at which the acid has completely interacted with or been neutralized by the base is called the equivalence point.
    • The indicators in acid-base titrations are compounds that have distinct hues in acidic and basic environments.

4.8 Redox Titrations

  • The transfer of electrons occurs in redox reactions, while the transfer of protons occurs in acid-base reactions.
  • We can titrate an oxidizing agent against a reducing agent in the same way that we can titrate an acid against a base.
    • When the reducing agent is oxidized by the oxidizing agent, the equivalence point is reached.
  • Because they have distinct hues in their oxidized and reduced forms, oxidizing agents can be utilized as an internal indicator in redox titration.
    • Acid-base neutralization require the same type of calculations as redox titrations.