CH 302 1st Edition Lecture 1 Outline of Current Lecture I. EnthalpyII. EntropyIII. Gibb’s Free EnergyCurrent LectureEnthalpy: 1. Which has a higher enthalpy, liquid water or gaseous water?- Gaseous water because there is more energy and it is less stable. 2. Why do different phases have different enthalpies?- Because of their Intermolecular Forces (IMFs)- Liquid: Molecules are close together, IMFs are attractive, and there is a lower enthalpy compared to molecules that are separated- Gas: Molecules are far apart and there are essentially no interactions. No IMFs mean higher energy3. Comparing isopropanol and acetone, which has the higher delta H of vaporization?- Isopropanol because it has stronger IMFs due to the H-bonding- Remember that H-bonding occurs between hydrogen and nitrogen, oxygen, or fluorineEnthalpy is related to the energy of a substance. Liquids have a lower enthalpy (because it has lower energy, so it is more stable). The stronger the IMFs are, the bigger the difference betweenthe liquid and the gas. Entropy:Which has a higher entropy, liquid water or gaseous water?- Gaseous water because there are more microstates than liquid water- Remember: entropy depends on the number of equivalent microstates in a systemImportant notes about entropy:- Entropy increases with increasing volume- Entropy increases with increasing temperature- Entropy increases with going from a solid to a liquid to a gas- The universe tends towards higher entropyComparing isopropanol and acetone, which has the greater delta S of vaporization?- They are about the same for almost every compound the difference in entropy between the liquid and the gas is the sameGibb’s Free Energy:Which has a lower gibb’s free energy, liquid water or gaseous water?- It depends on temperature because G = H – TSImportant notes about gibb’s free energy:- At equilibrium delta G = 0 and H = TS- The difference in boiling point result from the differences in IMF- The stronger the IMF, the bigger the enthalpy, the higher the
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