Chem 170 1st Edition Lecture 26Outline of Last Lecture I. Examples of Chemical EquilibriumII. Le Chatelier’s PrincipleOutline of Current Lecture I. Acids and BasesII. Auto Protolysis of WaterIII. pH = -log[H+]IV. Strong vs Weak Acids and Bases V. Examples Current LectureChapter 16 - Acids and BasesWater can disassociate into an acid and a base− ¿+¿+O H¿H2O ↔H¿Hydrochloric acid is a strong electrolyte−¿+¿+C l¿HCl↔ H¿Acetic acid is a weak electrolyte−¿+¿+CH3CO O¿CH2COOH ↔ H¿pH = -log[H+][H+] =10-pHAutoprotolysis of water/autoionization of water: −¿+¿+O H¿H2O ↔H¿− ¿+¿+O H¿2 H2O↔ H3O¿−237KJmol−237KJmol−135KJmol ΔGThese 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.−¿O H¿¿+¿H3O¿K = ¿∆ G=−RTln(K)∆ G=∑(n Gproducts0)−∑(nGreactants0)=[−237+(−157)]−2(−237)=80KJmolln(K)=−∆ GRT=−80000Jmol × K(8.314) (298)K=1 ×10−14Using pH = -log[H+]Consider +¿+OH2O ↔ H¿ where H+ and OH- equal x and Kw=1×10-14.+¿H¿¿−¿O H¿¿Kw=¿x=1× 10−7M+¿H¿¿pH=−log ¿Strong vs Weak Acids and Bases Strong acids and bases disassociate completelyStrong acid: HCl −¿+¿+C l¿HCl→ H¿ Strong base: NaOH −¿+¿+O H¿NaOH → N¿, where −¿O H¿ is the non-baseThe strength and the pH does not equal the corrosiveness or the counter ion.Weak acids and basesWeak acid: CH2COOH −¿+¿+CH3COO¿CH2COOH ↔ H¿Weak Base: −¿CH2COO¿−¿−¿+ H2O ↔CH3COOH +O H¿CH2COO¿Lewis Acid and Base DefinitionAcids are electron pair acceptors.Bases are electron pair donors.For example in the reaction −¿↔ H2O+¿+O H¿H¿ H+ gains an electron from OH- therefore H+ is the acid and OH- is the baseex. What is the pH of 0.015 M HCl solution?−¿+¿+C l¿HCl→ H¿HCl+¿H¿−¿C l¿0.015 M 0 0-x +x +x0.015-x=0 0+(0.015) 0+(0.015)pH=−log[0.015]=1.8ex. What is the pOH of the reaction −¿−¿+O H¿+¿+C l¿HCl+H2O ↔2 H¿, when the concentration of −¿O H¿ is (0.67×-12)0.67 ×10−12=12.2pOH =−log ¿note that pH +pOH = pKw
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