Chem112 Day 19.docx - Chemistry 112 \u2013 Day 19 Back to the 2nd Law o Explain why ice melting is spontaneous o Explain why water freezing is spontaneous

Chem112 Day 19.docx - Chemistry 112 u2013 Day 19 Back to...

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Chemistry 112 – Day 19 (11/06/2019)Back to the 2ndLawoExplain why ice melting is spontaneousoExplain why water freezing is spontaneousoWhat are we missing?oWe must consider system and surroundings. oSuniv= Ssys+ SsufAbsolute Entropy (s)oIn contrast to enthalpy we can get absolute values for S, not just S.oThe third law tells us that a perfect crystal at absolute zero has 0 entropy.oHow many microstates does this situation have?oWe can look up standard molar entropies SChange in entropy from 0K to 298KJ mol-1K-1Predicting Entropy ValuesoPhysical StatesoDissolving a solid or liquidMolecular solidsIonic solidsoDissolving a GasA dissolved gas will always have a lower entropy value than the gas itselfoAtomic Size and Molecular ComplexityLarger size means more microstatesEntropy increases with increasing complexityProblemsoWhich has the higher entropy of each pair?
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