Thermodynamics Unit

Rachel Todd
Mind Map by , created almost 6 years ago

Thermodynamics in AP Chemistry

Rachel Todd
Created by Rachel Todd almost 6 years ago
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Thermodynamics Unit
1 Energy
1.1.1 HEAT Change in system's energy ΔE = q + W System ex) a solution of HCL and another of NaOH were mixed together in a beaker with a stir rod Solution Chem: only the HCl and NaOH melecules (H+, OH-) Surrounds EVERYTHING ELSE What Causes Chemical Rxns? Free Energy ("nature of reactants") ΔG = ΔH - TΔS ΔG: the max amount of energy that can be used to do work ΔH: energy transferred as heat TΔS: energy used to create disorder - : thermodynamically favoured (spontaneous) + : NOT thermodynamically favoured Calculate #1: Calculate ΔH from calorimtry OR Hess's OR ΔHf; then calculate ΔS using entropy values; and then plug in to find ΔG at a certain temp #2: Calculate ΔG using ΔGfº values (ΔG = ΣnΔGº (products)−ΣnΔGº (reactants)) Entropy Δs: measure of disorder *more random wanted* 2nd law: Entropy of Universe is always increasing ΔS = S(products) - S(reactants) ΔSrxn = ΣnSº(products) - ΣnSº(reactants) Positive value is WANTED Enthalpy 1st Law of Thermodynamics: cannot be created or destroyed EXO ΔH = q = - ENDO ΔH = q = + can be calculated 4 ways #3 Hess's Law if a rxn is carried in 1 or several steps, the overall change in enthalpy is equal to the sum of the enthalpy changes for each step #2 Calorimeter Heat transfer cannot be directly measured Heat Capacity [kJ/K (or Cº)] Specific heat capacity: amount of heat needed to raise the temperature of 1 kg of a substance by 1 k [kJ/kg•K (or Cº)] ΔH rxn vs Δq rxn [ΔH = Δq/n] total amount of heat lost or gained by a rxn Using stoichiometry #1 Bond of Enthalpies Break bonds NEED energy For the image: A + B need energy to break up; C + D release energy when formed Form bonds REALEASE energy ΔH = ΣnBE - ΣnBE Σ = sum n = # of moles BE = bond energy *from exp't* values must be given #4 Enthalpy of Formation An arbitrary value that indicates how much heat would be lost/gained from experimental states ΔHº rxn=ΣnΔHºf (products)−ΣnΔHºf (Reactants) n: mol Most "Hº"'s will be given q (+): heat transferred IN q (-): heat transferred OUT w (+): work done ON the system w (-): work done BY the system ΔE is change in PE and KE of particles in a system
1.1.2 WORK W = -PΔV
1.2 PE
1.3 KE
1.3.1 Temperature Conversions C = K - 273 C = (5/9)(Fº - 32) a measure of the average KE of particles in a system If KE doubles, the temp doubles as well