Chemistry ch 2 lecture

Solution State and Pressure

• Understanding the behavior of solutions is critical in this course.

• Pressure affects solute solubility; lower pressure usually increases solute solubility in solutions.

Concentration Effects

• Concentrated solutions have molecules close together, leading to more interactions.

• Less concentrated solutions have molecules further apart, resulting in fewer interactions.

• Key values in concentration graphs:

  • q = 0: Represents a starting point.

  • q = ∞: Represents a theoretical maximum concentration.

Q Values and Activity

• The equation discussed involves activities, which relate to concentrations.

• If the concentration of any reactant (C or B) is zero, then q = 0.

• If one reactant (A or B) has a concentration of zero, then q = ∞.

• Valid q values range anywhere along the line between these extremes, where both reactants are present.

Reference Points

• The standard state is often defined in terms of a 1 molar concentration, and this sets our reference point where q = 1.

Delta G and Reaction Dynamics

• If q = 0, the Gibbs Free Energy ( \Delta G) equals the standard Gibbs Free Energy of the reaction.

• As you move along the graph from q=1, changing the value of q affects the slope, indicating how far the system is from equilibrium.

Equilibrium and the Constant K

• K is defined similarly to q, representing a specific ratio of products to reactants at equilibrium.

• The slope of the q line gives insights into energy levels and distance from equilibrium.

• There is only one specific value of q for which energy is minimized, and that is indicated by the equilibrium constant K.

Reaction Overview

• Reactions involving solids (s) or liquids (l) have concentrations for calculations; gases and solutions are considered in terms of their activity.

• To calculate \Delta G\ for a reaction:

  • Product activity values multiplied by their coefficients are summed.

  • Subtract the reactants' activity values multiplied by their coefficients.

  • Ensure no zero values are present in calculating \Delta S\ and \Delta H, for which an example results in \Delta S = -199 J/mol.

Delta G Calculations and Temperature

• \Delta G\ is dependent on temperature alongside concentrations and standard conditions.