CHEM 251 1st Edition Lecture 22 Outline of Last Lecture I. Clicker QuestionII. Lewis Acids and BasesIII. Predicting Acidity/BasicityIV. ReactivityV.Choosing SolventVI. Frustrated PairsOutline of Current Lecture VII. Clicker QuestionsVIII. Hard-Soft AcidsIX. Hard-Soft BasesX. Reactivity PredictionsXI. Application: Hydrogen StorageCurrent LectureXII. Clicker Questionsa. What is the strongest Lewis Acid? CCl4, SiCl4, GeCl4, SnCl4 XIII. Hard-Soft Acidsa. Hard acids: Characterized by low EN and high charge densityi. Alkali metalsii. Alkali earth metalsiii. Early transition metals (through Group 7 / Mn triad)iv. B, Al, Si, Ga, Geb. Soft acids: Characterized by high EN (for metals) and low charge densityi. Late transition metals, especially 2nd/3rd row (Cu, Pd, Ag, Au)ii. Heavy p-block metals (Hg, Tl, Pb)c. Borderline cases: hardness can be modulated based on conditionsi. Mostly late transition metals and mid-p-block cationsii. Metal oxidation state becomes a key factor: higher oxidation state (e.g. Cu(II) vs. Cu(I)) usually leads it larger charge density and harder Lewis acidsThese 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.XIV.Hard-Soft Basesa. Hard bases: High EN and high charge densityi. Fluoride (F–), oxide (O2–), hydroxide (OH–)ii. Other anionic oxygen-containing species (nitrate, phosphate, sulfate)iii. Small, non-polarizableb. Soft bases: Lower EN (for p-block) and lower charge densityi. Iodide (I–), sulfide (S2–), phosphide (P3–)ii. Polyatomics of these elements (R3C–, R2P–, RS–, etc.)iii. Large, polarizable anionsc. Borderline casesi. Chloride (harder), Bromide (softer)ii. Other miscellaneous cases of intermediate EN: N3–, NCS–iii. Unlike metal ions, which can have variable hardness, anion softness is fixediv. Complex anions may have multiple donors of different softnessXV. Reactivity Predictionsa. Like attracts likeb. Hard-hard and soft-soft preferredc. Hard-soft mismatchedd. Will reaction be endo or exothermic?i. Sc(OH)3(g) + InBr3(g) → In(OH)3(g) + ScBr3(g)ii. Answer: endothermic e. Hard-hard and soft-soft harder to break apartf. A combination of diffusing ions can “self-assemble” into most stable formXVI. Application: Hydrogen Storagea. Expensive and inefficientb. Compressed hydrogen, liquefied hydrogen, metal-organic frameworks, chemical
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