# Worksheets

• 1: Thermochemistry I (Worksheet)
In addition to mass changes, chemical reactions involve heat changes associated with changes in the substances’ internal energy. Like mass-based stoichiometry, these changes are quantitative. One of the most important physical relationships governing energy change is the First Law of Thermodynamics. Most often we will consider this in terms of a thermodynamic function called enthalpy.
• 2: Thermochemistry II (Worksheet)
As we saw last week, enthalpy and internal energy are state functions, which means that the sum of the heats of any set of steps that adds to give an overall reaction will have the same heat as doing the reaction directly -(Hess’s Law0. We will go on to see that if we use a special kind of thermochemical reaction, called the standard enthalpy of formation, we can calculate enthalpies of reactions without having to manipulate a series of individual thermochemical equations for each step.
• 3: Entropy and Probability (Worksheet)
This discussion worksheet addresses entropy as a measure of number of states available at a specific temperature. The distinction between macrostates and microstates is given within the context of individual molecules within a two-compartment system. Weights are introduced that quantify the number of microstates possible for an observed macrostate .This is connected to probability of its observation. Entropy is defined in terms of weights. A "disorder" argument is not invoked.
• 4: Second & Third Laws of Thermodynamics (Worksheet)
The three laws of thermodynamics describe restrictions on the behavior of virtually the entire physical world we can experience. Everything that is possible or impossible in a physical, chemical, or biological system is in some way related to these laws. We have previously talked about the First Law of Thermodynamics, which is concerned with the conservation of matter and energy. The Second and Third Laws are concerned with disorder and its relationship to spontaneous and non-spontaneous changes
• 5: Intermolecular Forces and Interactions (Worksheet)
This discussion worksheet addresses intermolecular forces separated into four categories: permanent-permanent electrostatic, permanent-induced electrostatic, instantaneous-induced electrostatic (London) and repulsive. These forces are discussed within Coulomb's law and connects forces to a potential energy. The distance dependence of each of the forces is given and multi-polar expansion. The application of different forces to specific systems is given and extension to experimental observables.
• 5A: Pure Phases and their Transitions (Worksheet)
This discussion worksheet addresses the phases of pure states and the transitions between phases. This includes both constant pressure and constant temperature changes. No introductory discussion is needed for students to complete.
• 5B: Solutions and Vapor Pressures (Worksheet)
This discussion worksheet addresses vapor pressure lowering and boiling point elevation in solutions (two of the four colligative properties commonly taught). The worksheet aims to draw the connection between depression of vapor pressure and increase of boiling point. A connection to entropy is proposed and the Raoult's law is discussed, including positive and negative deviations and the justifications for observing these non-ideal behavior.
• 6: Colligative Properties (Worksheet)
This discussion worksheet addresses the bases of the four colligative properties commonly tough: Vapor pressure lowering, melting point depression, boiling point elevation and osmotic pressure. An introduction to activity is given within the experimental context that the effective concentration in experimental colligative properties do not match the theoretical under high concentration. No background is needed to be discussed to complete the worksheet
• 7: Equilibria, Equilibrium Constants and Acid-Bases (Worksheet)
Knowing how to set up and solve equilibrium problems for gas-phase systems is essential preparation for applying equilibrium concepts to more complicated systems, such as acid-base chemistry. The mixture of reactants and products can often be altered by applying a stress to the system (changing species concentrations, changing pressures, changing temperature, etc.), and the shift in the position of the equilibrium can be understood and predicted on the basis of LeChatelier’s Principle.
• 8: ICE Tables (Worksheet)
This worksheet introduces and applies ICE tables to address the evolution of non-equilibrium conditions to equilibrium conditions. Emphasis is placed on understanding that the exact concentrations of species in a system under equilibrium can vary (depending on initial conditions), but since the equilibrium constant is fixed, then the relative concentrations will always be fixed. An introduction to ICE tables before this worksheet is beneficial, but not necessary.
• 9: Acids/Bases, Common Ion Effect, and Buffers (Worksheet)
This worksheet address three aspects: The definition of solubility is given along with a Le Châtelier perspective to understand why an equilibrium cannot be established when Q < Ksp. The common ion effect is then introduced to reduce apparent solubility. Then acid/base equilibria of acetic acid is introduced and a common ion effect in this case is explore (conjugate base). The pH of a solution with this "buffer" and without is compared. The Henderson-Hasselbalch equation is NOT introduced.
• 10: Weak Acid and Base Equilibria (Worksheet)
We have seen that the calculation of [H₃O⁺] and pH for solutions of strong acids and base. To carry out a calculation of all species present in a solution of a pure weak acid in water requires use of the equilibrium constant for the acid’s hydrolysis, called Ka. The strengths of acids and their conjugate bases are related to their molecular structures. Knowing the trends allows us to predict whether an acid is strong or weak, and if weak how it compares in strength to other similar weak acids.