Equilibrium Chemistry Quiz

Equilibrium Chemistry

• Students are expected to analyze reversible reactions, chemical equilibria, and thermodynamics.
• Students are expected to compute worded problems related to equilibrium chemistry.
• Students are expected to appreciate the importance of equilibrium chemistry.

Reversible Reactions and Chemical Equilibria

• In 1798, chemist Claude Berthollet accompanied Napoleon's military expedition to Egypt.
• Berthollet observed deposits of Na2CO3 at the Natron Lakes, which surprised him.
• This observation contributed to an important discovery about reversible chemical reactions.
• Chemical reactivity was once explained by the concept of "elective affinities".
• Berthollet's reasoning highlighted that reactions are reversible.
• Chemical reactions can move in both directions, determined by the relative amounts of reactants and products.
• The reversibility of a reaction is shown using a double arrow in an equation.

Thermodynamics and Equilibrium Chemistry

• Thermodynamics studies thermal, electrical, chemical, and mechanical forms of energy.
• The study of thermodynamics is important in chemistry.
• A reaction's free energy (∆G) is a function of its enthalpy (∆H), entropy (∆S), and temperature (T).
• The Gibb's free energy function (∆G = ∆H - T∆S) is used to determine if a reaction is thermodynamically favorable.
• A negative ∆G indicates a favorable reaction, while a positive ∆G indicates an unfavourable reaction.

Equilibrium Constants for Chemical Reactions

• Equilibrium constant (K) defines the reaction's equilibrium position.
• K is the ratio of product concentrations to reactant concentrations, each raised to their stoichiometric coefficients.
• At equilibrium, the free energy (∆G) is zero.
  • Thus, ∆G° = -RTlnK

Manipulating Equilibrium Constants

• Reversing a reaction reverses the equilibrium constant.
• Adding reactions multiplies their equilibrium constants.

Precipitation Reactions

• Precipitation reactions involve the formation of an insoluble precipitate from two soluble ions.
• The reaction is often a metathesis reaction.
• The equilibrium constant for precipitation reactions is the solubility product (Ksp).

Acid-base Reactions

• Acids donate protons, and bases accept protons.
• The most common strong acids are HCl, HI, HBr, HNO3, and HClO4, etc.
• The strongest acid in any given set is one that will readily donate its proton to the solvent or another molecule.
• Acids and bases can be strong or weak.
• Equilibrium constant expressions include concentrations of reactants and products in the reaction, each raised to their stoichiometric coefficients.
• Equilibrium constants are often called dissociation constants for the reactant-product reactions (Ka).
• The magnitude of Ka provides information about its relative strength.

Complexation Reactions

• In complexation reactions, metal ions act as electron acceptors, and a ligand acts as an electron donor.
• The equilibrium constant expresses the stability of the resulting metal-ligand complex, often called a formation constant (Kf).
• The reverse of a complexation reaction yields a dissociation constant (Kd).
• Kf and Kd are reciprocals of each other.

Redox Reactions

• Oxidation/Reduction Reactions involve electron transfer between reactants.
• A change in oxidation state indicates either oxidation or reduction.
• The species being oxidized is the reducing agent, and the species being reduced is the oxidizing agent.
• Equilibrium constants for redox reactions are often expressed as standard electrode potentials (E°).

Test your knowledge on reversible reactions, chemical equilibria, and thermodynamics in this Equilibrium Chemistry Quiz. Analyze different scenarios and compute worded problems to appreciate the significance of equilibrium in chemical reactions.