University:
Eastern Kentucky University
Course:
CHE 111 | General Chemistry
Academic year:

2020
Views:

12

Pages:

1
Author:

Lance Gutierrez

General Chemistry 7: Thermochemistry Systems and Processes Temperature (T) and Heat (q) Isolated System: Exchange neither matter nor energy with the environment. Temperature (T): Scaled measure of average kinetic energy of a substance. Closed System: Can exchange energy but not matter with the environment. Open system: Can exchange BOTH energy and matter with the environment. Isothermal Process: Constant temperature. Adiabatic Process: Exchange no heat with the environment. % ℉=($ Celsius vs 0°C = 32°F Fahrenheit: 25°C = 75°F & ℃$)+32 Freezing Point H2O Room Temp 37°C = 98.6°F Body Temp Heat (q): The transfer of energy that results from differences of temperature. Hot transfers to cold. Isobaric Process: Constant pressure. Isovolumetric: Constant volume. (isochoric) Enthalpy (H) Enthalpy (H): A measure of the potential energy of a system found in intermolecular attractions and chemical bonds. States and State Functions State Functions: Describe the physical properties of an equilibrium state. Are pathway independent. Pressure, density, temp, volume, enthalpy, internal energy, Gibbs free energy, and entropy. Standard Conditions: 298 K, 1 atm, 1 M Note that in gas law calculations, Standard Temperature and Pressure (STP) is 0°C, 1 atm. Fusion: Solid liquid Freezing: Liquid Vaporization: Liquid solid gas Sublimation: Solid gas Deposition: Gas solid Phase Changes: Solid Liquid Gas: ENDOTHERMIC since gases have more heat energy than liquids and liquids have more heat energy than solids. Gas Liquid Solid: EXOTHERMIC since thes reactions release heat. Hess’s Law: Enthalpy changes are additive. ° $from heat of formations D𝐻-./ ° ° ∆𝑯𝐫𝐱𝐧 =$∆𝑯𝐩𝐫𝐨𝐝𝐮𝐜𝐭𝐬 −$∆𝑯°𝐫𝐞𝐚𝐜𝐭𝐚𝐧𝐭𝐬 D𝐻-./° $from bond dissociation energies ° ° ° ∆𝑯𝐫𝐱𝐧 =$∆𝑯𝐫𝐞𝐚𝐜𝐭𝐚𝐧𝐭𝐬 −$∆𝑯𝐩𝐫𝐨𝐝𝐮𝐜𝐭𝐬 Entropy (S) Triple Point: Point in phase diagram where all 3 phases exist. Supercritical Fluid: Density of gas = density of liquid, no distinction between those two phases. Entropy (S): A measure of the degree to which energy has been spread throughout a system or between a system and its surroundings. @ ∆𝑆 =$ ABC D Standard entropy of reaction ° ° ∆𝑺𝐫𝐱𝐧 =$∆𝑺𝐟,𝐩𝐫𝐨𝐝𝐮𝐜𝐭𝐬 −$∆𝑺°𝐟,𝐫𝐞𝐚𝐜𝐭𝐚𝐧𝐭𝐬 Note: Entropy is maximized at equilibrium. Gibbs Free Energy (G) Gibbs Free Energy (G): Derived from enthalpy and entropy. D 𝑮=$ D𝐇−𝐓$ D𝐒 Gibbs Free Energy (G) D𝑮=$ D𝐇−𝐓$ D𝐒 DH DS Outcome + + Spontaneous at HIGH temps + - Non-spontaneous at all temps - + Spontaneous at all temps - - Spontaneous at LOW temps Note: Temperature dependent when DH and DS have same sign. Standard Gibbs free energy of reaction ° ° D𝑮𝐫𝐱𝐧 =$∆𝑮𝐟,𝐩𝐫𝐨𝐝𝐮𝐜𝐭𝐬 −$∆𝑮°𝐟,𝐫𝐞𝐚𝐜𝐭𝐚𝐧𝐭𝐬 From equilibrium constant Keq ° =$−R$𝑇$ln$(𝐾VW) ∆𝐺MNO From reaction quotient Q ° +$R$𝑇$ln$(𝑄) ∆𝐺MNO=∆𝐺MNO Y ∆𝐺MNO=R$𝑇$ln$( ) ZB[ D G < 0 :Spontaneous D G = 0 : Equilibrium D G > 0 : Non-spontaneous