CHEM 433 FALL 2011 EXAM #2 REVIEW SHEET SCOPE: Lecture through first half of W 10/12/11. Atkins Chapter 2. HW#3 & #4 (or perhaps “4” and “4” !) FORMAT: As before, a page of MC, 1 or 2 written problems (i.e. “math”), and 1 or 2 short answer ( i.e. “words & pictures”, where “words” means reasonably complete sentences, not just brief statements of terms. But brevity is something to strive for.) As always, be prepared to obtain a mathematical result and interpret it or explain its significance. PROTOCOL: As before. 50 minutes in class, you can bring 1 note car with whatever you want to put on it. TERMS Thermodynamics Endothermic Process Sublimation System Isothermal Process Thermochemical Equation Surroundings Adiabatic Process Standard Reaction Enthalpy Universe Expansion Work Standard Combustion Enthalpy Open system Reversible Change Hess’ Law Closed system Indicator diagram (P vs. V) Standard Enthalpy of Formation Isolated system Constant Volume Heat Capacity Reference State Adiabatic barrier Enthalpy State Function Diathermic barrier Constant pressure heat capacity Path Function 1st Law of THERMO Adiabat Internal Pressure Internal Energy Adiabatic Change Thermal Expansion Coefficient Work Thermochemistry Isothermal Compressibility Heat Standard State Joule Thompson Coefficient State Function Standard Enthalpy Changes Isothermal J-T Coefficient Path Functions Fusion Exothermic Process Vaporization CONCEPTS 1st Law of Thermo – the core ideas: Conceptual significance of the 1st Law as adapted for chemists (e.g. Do molecules have heat or work? Can we measure U directly?). Expansion work: calculating 3 simple cases. Heat capacities/heat transfer: relating temperature changes to energy changes (Can you calculate the numbers and/or derive the expressions for the three cases we discussed in class?). Exploiting the first law to determine q, w, and DU for a “process” – heating/cooling, expansion/contraction or a cycle – usually these involve ideal gases. Can you draw or interpret pictures of the heat/energy flow for simple processes? Recognizing these processes on an indicator diagram (i.e. plot of p vs. V)? Enthalpy: What is the advantage of H (vs. U) when dealing with a constant pressure system – i.e. what does it account for? How does it differ from U? Adiabatic Expansion: How does this process differ from isothermal? Reversible vs. constant (external) pressure, isothermal vs. adiabatic etc. Can you describe the heat and work flow in each case? Difference between Cv and Cp – which is bigger (always) and why? Thermochemistry: Two consequences of H being a state function, two consequences of H being an extensive property. Rationalizing trends in ΔH for physical process on the basis of intermolecular (a.k.a. physical) forces. ΔH for chemical changes: Calculating ΔrH° using Hess’ Law or Heats of Formation. Relating ΔrH° to ΔrU°. Temperature dependence of ΔrH° - calculating ΔH at some other temperature – both for constant Cp’s (i.e. small ΔT) and for Cp(T) (usually large ΔT). 1st Law “Machinery”: Physical rationale for the internal pressure and Joule-Thompson effect in terms of IMF. Using “1st law quantities” (a, κT, µ, etc.) to calculate changes in the values of the properties they relate. Manipulating differentials of U and H (i.e. the Internal Energy and Enthalpy “safaris”) to obtain new quantities, and in turn, to obtain the partial derivatives that are analogous to C and C – but have the other variable held constant (e.g. ⎛ ∂U ⎞ ). Using derivative v p ⎜ ⎟ ⎝ ∂T ⎠ p st expressions for the 1 Law quantities and an equation of state to derive values/expressions for a specific system (e.g. κT for an ideal gas). Calculating (estimating) changes using simplified expressions (i.e. w/ Δ’s) for a, κT, m to calculate changes in various quantities (these are all physical processes). Deriving and interpreting€ relationships between Cp and Cv (ideal gas and in general), and the physical significance of the expression(s)for Cp–Cv. .