CHEM 102 1nd Edition Lecture 7 Outline of Previous Lecture I. Bond EnergyII. ThermodynamicsIII. First Law of ThermodynamicsOutline of Current LectureI. Enthalpy EquationsII. Thermodynamics DefinitionsIII. Natural Tendencies for DisorderIV. EntropyV. Example of EntropyCurrent LectureI. Enthalpy Equations- At constant P, ΔH = ΔE + PΔV (or any other equation for work)- Gases at fixed temperature, ΔH = ΔE + (Δn)RTII. Thermodynamics Definitions- Thermodynamics: dictate direction of the reaction- Thermochemistry: determining the heat of the reaction- Kinetics: determines the speed of the reaction- Equilibrium: extent of reaction- Spontaneous: a reaction that only occurs without continual energy input, the sign for spontaneity is positiveo Example in class; of the three balloons in class (one Oxygen, one Hydrogen, one Oxygen/Hydrogen) the one with Oxygen only exploded after the flame was held to the balloon for an extended period of time, the other two exploded almost immediately; therefore, the HydrSogen and Oxygen/Hydrogen balloons are spontaneous- Nonspontaneous: the reaction will not occur by itself and must have continual energy input for the reaction to occur, the sign for nonspontaneity is negativeo Example in class; the oxygen balloon is nonspontaneous because it required a flame the entire time in order for the reaction to occur. o Most of the time a reaction is spontaneous one way but nonspontaneous the other way.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.III. Natural Tendencies for Disorder- Spontaneity occurs in the direction that disorder increases- If a reaction goes from disorder to nondisorder, the reaction is less spontaneous- Gas to solid, spontaneous to nonspontaneousIV. Entropy- The measure of disorder; greater disorder, greater entropy- ΔSuniv = ΔSsys + ΔSsurr (always greater than 0)- If reaction is spontaneous, entropy of the universe is increasing- Trends of Entropyo More bonds, more entropyo Entropy increases from solid to liquid to gas (gas has most intropy)o A solution has more entropy than a solvent and solute separate o More entropy after the gas expandso As temperature increases, entropy increaseso As volume increases, entropy increaseso As number of atoms increases, entropy increasesV. Example of Entropy- Which has the decrease in disorder?o CH4(g) + 2O2(g) CO2(g) + 2H2O(g)o CO2(s) CO2(g)o NO2(g) compared to N2O4(g)o 2H2(g) + O2(g) 2H2O(g)
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