Lewis Acids and Bases

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Lewis Acids and Bases Tro Chapter 16 – Acids and Bases Section 16.11 – Lewis Acids and Bases Lewis Acid–Base Theory • Lewis acid–base theory focuses on transferring an electron pair. • Lewis acid—lone pair acceptor • Lewis base—lone pair donor • Does not require H+ Lewis Acids • They are electron deficient, either from being attached to electronegative atom(s) or not having an octet. • They must have an empty orbital willing to accept the electron pair. • H+ has empty 1s orbital. • B in BF3 has empty 2p orbital and an incomplete octet. • Many small, highly charged metal cations have empty orbitals that they can use to accept electrons. • Atoms that are attached to highly electronegative atoms and have multiple bonds can be Lewis acids. Lewis Bases • The Lewis base has electrons it is willing to give away to or share with another atom. • The Lewis base must have a lone pair of electrons on it that it can donate. • Anions are better Lewis bases than neutral atoms or molecules. • N: < N:− • Generally, the more electronegative an atom, the less willing it is to be a Lewis base. • O: < S: Lewis Acid–Base Reactions • The base donates a pair of electrons to the acid. • It generally results in the formation of a covalent bond. H3N: + BF3 H3N─BF3 • The product that forms is called an adduct. • Arrhenius and Brønsted–Lowry acid–base reactions are also Lewis reactions. Lewis Acid / Base Reactions Examples of Lewis Acid–Base Reactions Examples of Lewis Acid–Base Reactions junk Metal Cations as Weak Acids 3+ 2+ + Al(H2O)6 (aq) + H2O(l) Al(H2O)5(OH) (aq) + H3O (aq) Tro, Chemistry: A Molecular Approach 10.

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Acids Lewis Acids and Bases Lewis Acids Lewis Acids: H+ Cu2+ Al3+ Lewis Bases
E5 Lewis Acids and Bases (Session 1) Acids November 5 - 11 Session one Bronsted: Acids are proton donors. • Pre-lab (p.151) due • Problem • 1st hour discussion of E4 • Compounds containing cations other than • Lab (Parts 1and 2A) H+ are acids! Session two DEMO • Lab: Parts 2B, 3 and 4 Problem: Some acids do not contain protons Lewis Acids and Bases Example: Al3+ (aq) = ≈ pH 3! Defines acid/base without using the word proton: + H H H • Cl-H + • O Cl- • • •• O H H Acid Base Base Acid . A BASE DONATES unbonded ELECTRON PAIR/S. An ACID ACCEPTS ELECTRON PAIR/S . Deodorants and acid loving plant foods contain aluminum salts Lewis Acids Lewis Bases . Electron rich species; electron pair donors. Electron deficient species ; potential electron pair acceptors. Lewis acids: H+ Cu2+ Al3+ “I’m deficient!” Ammonia hydroxide ion water__ (ammine) (hydroxo) (aquo) Acid 1 Lewis Acid-Base Reactions Lewis Acid-Base Reactions Example Metal ion + BONDED H H H + • to water H + • O O • • •• molecules H H Metal ion Acid + Base Complex ion surrounded by water . The acid reacts with the base by bonding to one molecules or more available electron pairs on the base. The acid-base bond is coordinate covalent. The product is a complex or complex ion Lewis Acid-Base Reaction Products Lewis Acid-Base Reaction Products Net Reaction Examples Net Reaction Examples 2+ 2+ + + Pb + 4 H2O [Pb(H2O)4] H + H2O [H(H2O)] Lewis acid Lewis base Tetra aquo lead ion Lewis acid Lewis base Hydronium ion 2+ 2+ 2+ 2+ Ni + 6 H2O [Ni(H2O)6] Cu + 4 H2O [Cu(H2O)4] Lewis acid Lewis base Hexa aquo nickel ion Lewis acid Lewis base Tetra aquo copper(II)ion DEMO DEMO Metal Aquo Complex Ions Part 1.
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Lesson 21: Acids & Bases
Lesson 21: Acids & Bases - Far From Basic Lesson Objectives: • Students will identify acids and bases by the Lewis, Bronsted-Lowry, and Arrhenius models. • Students will calculate the pH of given solutions. Getting Curious You’ve probably heard of pH before. Many personal hygiene products make claims about pH that are sometimes based on true science, but frequently are not. pH is the measurement of [H+] ion concentration in any solution. Generally, it can tell us about the acidity or alkaline (basicness) of a solution. Click on the CK-12 PLIX Interactive below for an introduction to acids, bases, and pH, and then answer the questions below. Directions: Log into CK-12 as follows: Username - your Whitmore School Username Password - whitmore2018 Questions: Copy and paste questions 1-3 in the Submit Box at the bottom of this page, and answer the questions before going any further in the lesson: 1. After dragging the small white circles (in this simulation, the indicator papers) onto each substance, what do you observe about the pH of each substance? 2. If you were to taste each substance (highly inadvisable in the chemistry laboratory!), how would you imagine they would taste? 3. Of the three substances, which would you characterize as acid? Which as basic? Which as neutral? Use the observed pH levels to support your hypotheses. Chemistry Time Properties of Acids and Bases Acids and bases are versatile and useful materials in many chemical reactions. Some properties that are common to aqueous solutions of acids and bases are listed in the table below. Acids Bases conduct electricity in solution conduct electricity in solution turn blue litmus paper red turn red litmus paper blue have a sour taste have a slippery feeling react with acids to create a neutral react with bases to create a neutral solution solution react with active metals to produce hydrogen gas Note: Litmus paper is a type of treated paper that changes color based on the acidity of the solution it comes in contact with.
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Acids and Bases
self study Most of this is probably background from a prior chemistry course; some near the end is GG325 review Aqueous Inorganic Geochemistry of Natural Waters Three important topics: 1. Acids, bases and the aqueous CO 2 system 2. Behavior of ions in aqueous solution 3. Quantifying aqueous solubility and total dissolved solids (TDS) Pease read Manahan chapter 3 and review chapter 28 (6 th Ed) for next week GG425 Wk2, S2016 Acids and Bases GG425 Wk2, S2016 1 1. Two Types of Acids and Bases: a. Brönstead acids and bases contain H + and OH - HCl ↔ H + + + Cl- (acid) NaOH ↔ Na + + OH - (base). + - water is acid and base simultaneously, H 2O ↔ H + OH . pure water and acid neutral aqueous solutions have equal amounts of H + and OH -. b. Lewis acids and bases Brönstead acids can be thought of as electron deficient ions and bases as electron excessive ions , which provides a different perspective on acidity/basisity that we can extend to other (non protic and non hydroxyl) compounds. We call this the Lewis acid/base concept. GG425 Wk2, S2016 Brönstead acidity: Kw is the equilibrium constant for the dissociation of water. + - H2O ↔ H + OH + - -14 Kw = [H ][OH ] = 10 at 25 EC Kw has a slight temperature dependence: Temp ( EC) Kw 0 10 -14.94 less dissociated 25 10 -14 60 10 -13.02 more dissociated GG425 Wk2, S2016 2 Brönstead acidity: + - H2O ↔ H + OH + - Kw = [H ][OH ] An acid neutral solution always has [H +] = [OH -]. Setting [H +] = x, yields x 2= 10 -14 x = 10 -7 = moles of H + in this solution.
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General Chemistry/Properties and Theories of Acids and Bases 1 General Chemistry/Properties and Theories of Acids and Bases
General Chemistry/Properties and Theories of Acids and Bases 1 General Chemistry/Properties and Theories of Acids and Bases Acid-Base Reaction Theories Acids and bases are everywhere. Some foods contain acid, like the citric acid in lemons and the lactic acid in dairy. Cleaning products like bleach and ammonia are bases. Chemicals that are acidic or basic are an important part of chemistry. Helpful Hint! You may need to refresh your memory on naming acids. Several different theories explain what composes an acid and a base. The first scientific definition of an acid was proposed by the French chemist Antoine Lavoisier in the eighteenth century. He proposed that acids contained oxygen, although he did not know the dual composition of acids such as hydrochloric acid (HCl). Over the years, much more accurate definitions of acids and bases have been created. Arrhenius Theory The Swedish chemist Svante Arrhenius published his theory of acids and bases in 1887. It can be simply explained by these two points: Arrhenius Acids and Bases 1. An acid is a substance which dissociates in water to produce one or more hydrogen ions (H+). 2. A base is a substance which dissociates in water to produce one or more hydroxide ions (OH-). Based on this definition, you can see that Arrhenius acids must be soluble in water. Arrhenius acid-base reactions can be summarized with three generic equations: Svante Arrhenius General Chemistry/Properties and Theories of Acids and Bases 2 An acid will dissociate in water producing hydrogen ions. A base (usually containing a metal) will dissociate in water to product hydroxide ions.
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Acids and Bases
Acids and Bases 362 2020 Lecture 15 Lewis approach to acid/base interactions Gilbert Newton Lewis 1875 – 1946 Lewis Concept Lewis, 1930s: Base is a donor of an electron pair. Acid is an acceptor of an electron pair. For a species to function as a Lewis acid, it needs to have an accessible empty orbital. For a species to function as a Lewis base it needs to have an accessible electron pair. + + 6+ Examples of Lewis acids: BF3, AlCl3, SbF5, Na , H , S , etc. - Examples of Lewis bases: F , H2O, Me3N, C2H4, Xe, etc. Lewis Continued A more general view also classifies compounds that can generate a species with an empty orbital as Lewis acids. Then we can include B2H6, Al2Cl6, HCl etc. Since H+ and any cation from a solvent autodissociation is a Lewis acid, and anything that can add H+ or a solvent- derived cation is a Lewis base, the Lewis acid concept effectively includes the ones discussed previously. Lewis Continued Acid-base reactions under the Lewis model are the reactions of forming adducts between Lewis acids and bases. BF3 + Me3N F3B-NMe3 HF + F- FHF- - 2- SiF4 + 2F SiF6 - - CO2 + OH HCO3 TiCl4 + 2Et2O TiCl4(OEt2)2 In fact, any chemical compound can be mentally disassembled into Lewis acids and bases: 6+ - S + 6F SF6 4+ - - + - C + 3H + NH2 CH3 + NH2 Lewis Acids & Bases Other good examples involve metal ions. ••• •O—H 2+ •• 2+ Co • O—H Co • H ACID BASE H 2+ [Co(H2O)6] Empty d2sp3 hybrids on Cobalt account for the Lewis Acid/Base interactions Lewis Acids & Bases The combination of metal ions (Lewis acids) with Lewis bases such as H2O and NH3 ------> COMPLEX IONS All metal ions form complex ions with water —and are of n+ the type [M(H2O)x] where x = 4 and 6.
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Acids and Bases—Chapter 4 Shriver et al. MIT 3091 Video Lecture: Acids and Bases on You Tube http://ocw.mit.edu/courses/materials-science-and-engineering/3-091sc- introduction-to-solid-state-chemistry-fall-2010/aqueous-solutions/26- acids-and-bases/ Acid-Base concepts Gilbert Newton Lewis 1875 – 1946 Lewis Concept Lewis, 1930s: Base is a donor of an electron pair. Acid is an acceptor of an electron pair. For a species to function as a Lewis acid, it needs to have an accessible empty orbital. For a species to function as a Lewis base it needs to have an accessible electron pair. + + 6+ Examples of Lewis acids: BF3, AlCl3, SbF5, Na , H , S , etc. - Examples of Lewis bases: F , H2O, Me3N, C2H4, Xe, etc. Lewis Concept—Connection to MO Theory Lewis, 1930s: Base is a donor of an electron pair. Acid is an acceptor of an electron pair. For a species to function as a Lewis acid, it needs to have an accessible empty orbital. For a species to function as a Lewis base it needs to have an accessible electron pair. Examples of Lewis acids: BF3, AlCl3, + + 6+ SbF5, Na , H , S , etc. - Examples of Lewis bases: F , H2O, Me3N, C2H4, Xe, etc. Lewis Continued A more general view also classifies compounds that can generate a species with an empty orbital as Lewis acids. Then we can include B2H6, Al2Cl6, HCl etc. Since H+ and any cation from a solvent autodissociation is a Lewis acid, and anything that can add H+ or a solvent- derived cation is a Lewis base, the Lewis acid concept effectively includes the ones discussed previously.
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Why study acids & bases? Chapter 14: Acids,Bases and Salts ❖Many household substances, including cleaning solutions and food/beverages Sections 14.1 – 14.5 that we consume, are acids or bases. CHM152 GCC ❖ In the environment, the pH of rain, water and soil can also have significant effects. ❖Acid – base reactions occurring in our body are essential for life. They are also OpenSTAX: Chemistry involved in many industrial processes. 1 2 Acid vs. Base Characteristics Acid-Base Models Acids Bases CHM 150/151 taught Arrhenius theory ▪ Taste sour ❑ Taste bitter, chalky Acids produce hydrogen ions in water ▪ Corrode most metals ❑ Feel soapy, slippery ▪ HA (aq) → H+ (aq) + A- (aq) ▪ Turn litmus paper red ❑ Turn litmus paper blue Bases produce hydroxide ions in water ▪ MOH (aq) M+ (aq) + OH- (aq) ▪ Have low pH’s ❑ Have high pH’s → ▪ E.g. vinegar, lemon juice, ❑ E.g. milk of magnesia, CHM 152 uses Brønsted-Lowry theory gastric juice, soft drinks bleach, ammonia, drano Bronsted Acid: Substance that can donate H+ Acid loses H+ Bronsted Base: Substance that can accept H+ Base gains H+ 3 4 Bronsted-Lowry Reactions involve the Bronsted Acids and Bases transfer of 1 H+ A conjugate acid is formed when a Brønsted A conjugate base is formed when a Brønsted base accepts a proton. acid loses a proton. Gains a proton Loses a proton Gains a proton Loses a proton + – + – NH3(aq) + H2O(l) ⇌ NH4 (aq) + OH (aq) HCl(aq) + H2O(l) ⇌ H3O (aq) + Cl (aq) base acid conjugate conjugate acid base conjugate conjugate acid base acid base conjugate pair: differ by 1 H+ ion Note: Water is amphoteric – it can act as an acid or a base depending on what its reacting with.
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5.03, Inorganic Chemistry Prof. Daniel G. Nocera Lecture 6 Apr 11: Acid-Base Chemistry Gas-Phase Acid-Base Reactions The most straightforward acid-base reaction occurs by attack of H+ on an atom or + molecule (B) in the gas phase. Consider the attack of H on H2 to produce the + simplest polyatomic molecule, H3 (which has been detected by mass spectrometry in electrical discharges of H2 gas). H+ attacks the HOMO of the base B for any protonation in the gas phase. For the example above, the bonding situation is described as follows: 1 + The difference in the bond dissociation energies of H2 and H3 gives the energy for + H association to H2, + + + –1 H3 → 2H + H ∆H1 = BDE(H3 ) = 203 kcal mol –1 H2 → 2H ∆H2 = BDE(H2) = 103 kcal mol Thus the energy for protonation is + + 2H + H → H3 H2 → 2H + + –1 H2 + H → H3 ∆Hassoc = ∆H2 – ∆H1 = –100 kcal mol and therefore the protonation of H2 is comparable to its bond strength. The proton affinity (PA) is the energy released upon attack of H+ on a species B in the gas phase, + + B + H → BH PA = –∆Hassoc by convention, a positive value is exothermic Can divide the protonation reaction in to two hypothetical reactions + + B + H → B + H ∆H1 = IE(B) – IE(H) + + + B + H → BH ∆H2 = –BDE(BH ) + + + B + H → BH ∆Hassoc = IE(B) – IE(H) – BDE(BH ) PA = IE(H) – IE(B) + BDE(BH+) PA = 13.598 eV – IE(B) + BDE(BH+) Protonation of B is therefore favored for small IE(B) … i.e., for small ionization energies of electrons in HOMO (or in other terms, electrons in higher energy HOMO are more easily attacked by the proton) and large bond dissociation energies.
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Conjugate Acid Base Pairs • Conjugate Base: Formed from an Acid When It Donates a Proton to a Base
Acids and Bases Dr. Sapna Gupta Arrows in Organic Chemistry synthesis (yield) equilibrium resonance retrosynthesis (backward) transfer of two electrons transfer of one electron Dr. Sapna Gupta/Acids and Bases 2 Acids and Bases • A Brønsted acid donates a hydrogen cation (H+) • A Brønsted base accepts the H+ • “proton” is a synonym for H+ - loss of an electron from H leaving the bare nucleus— a proton • Full headed arrows indicate transfer of electrons. Example Dr. Sapna Gupta/Acids and Bases 3 Conjugate Acid Base Pairs • Conjugate base: formed from an acid when it donates a proton to a base. A strong acid gives a weak conjugate base and vice versa. • Conjugate acid: formed from a base when it accepts a proton from an acid. A strong base gives a weak conjugate acid and vice versa. conjugate acid-base pair conjugate acid-base pair - + HCl( aq) + H2 O( l) Cl ( aq) + H3 O ( aq) Hydrogen Water Chloride Hydronium chloride ion ion (acid) (base) (conjugate (conjugate base of HCl) acid of H 2O) conjugate acid-base pair conjugate acid-base pair - + CH3 COOH + NH3 CH3 COO + NH4 Acetic acid Ammonia Acetate Ammonium ion ion (acid) (base) (conjugate base (conjugate acid Dr. Sapna Gupta/Acidsacetic acid)and Bases of ammonia) 4 Examples of Acids and Bases • There are inorganic (mineral) and organic acids and bases. Dr. Sapna Gupta/Acids and Bases 5 Solved Problems 1) What is conjugate acid of NH3? 2) What are the conjugate bases in the reaction below? a) NH2 + 2 2 b) NH2 CO3 + HSO4 HCO3 + SO4 - c) NH2 d) NH4 a) HCO3 and HSO4 + 2 e) NH4 b) HSO4 and CO3 2 c) CO3 and OH 2 d) SO4 and HSO4 2 2 e) CO3 and SO4 3) For the reaction below which two 4) A strong acid leads to a substances which are both acids a) weak conjugate acid + + CH3NH3 + H2O CH3NH2 + H3O b) strong conjugate base c) weak conjugate base + a) H2O and H3O d) strong base + b) CH3NH3 and H2O e) pure water + c) CH3NH3 and CH3NH2 + + d) CH3NH3 and H3O e) CH3NH2 and H2O Dr.
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Acid Base Concepts
Page 1 Acid Base Concepts The Swedish chemist, Svante Arrhenius, framed the first successful concept of acids and bases. He defined acids and bases in terms of their effect on water. According to Arrhenius, acids are substances that increase the concentration of H+ ions in aqueous solution, and bases increase the concentration of OH- ions in aqueous solution. But many reactions that have characteristics of acid-base reactions in aqueous solution occur in other solvents or no solvent at all. The Bronsted-Lowry and Lewis concepts of acids and bases apply to nonaqueous as well as aqueous solutions and also enlarge on the Arrhenius concept. Arrhenius concept acids: Hydrogen ion (H+) donors H2O + - HCl(g) H (aq) + Cl (aq) Bases: Hydroxide ion (OH-) donors. H2O + - NaOH(s) Na (aq) + OH (aq) Hydronium Ion In reality, H+ ions do not float around in aqueous solution. Instead, they always attach themselves to a water + molecule forming the hydronium ion, H3O . So a more accurate representation of the dissociation of HCl above would be: + - HCl + H2O H3O + Cl For simplicity's sake, many texts will leave the water out of these dissociation equations assuming that the + + student knows that H (aq) really means H3O (aq). + - HCl H (aq) + Cl (aq) In the Arrhenius concept, when an acid and a base are mixed, the result is water (formed from the H+ and the OH-) and a "salt" (composed of the leftover cation of the base and the leftover anion of the acid). For example HCl + NaOH H2O + NaCl acid base water "salt" This type of neutralization reaction occurs with any Arrhenius acid and base.
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GRADES 6-12 DISTANCE LEARNING School Name Aledo High School
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Acids, Bases and Solution Equilibria
Acids, bases and solution equilibria A four lecture course for the 1st year Jose M. Goicoechea http://course.chem.ox.ac.uk/acids-bases-and- solutions-equilibria-year-1-2014.aspx http://goicoechea.chem.ox.ac.uk/teaching.html Acid-base reactions + + NH3 + H3O NH4 + H2O + - H2O + HI H3O + I - 2- + HSO4 + H2O SO4 + H3O NH3 + BF3 NH3:BF3 C5H5N + I2 C5H5N:I2 Species highlighted act as acids Redox reactions A redox reaction is a reaction in which there is a change in oxidation state Fe3+(aq) + Cr2+(aq) Fe2+(aq) + Cr3+(aq) + 2+ Zn(s) + 2H3O Zn + H2(g) 2PCl3 + O2 2OPCl3 Ca(s) + H2 CaH2(s) + - O2 + Pt + 3F2 [O2] [PtF6] One or two electrons are transferred entirely Species highlighted act as oxidants Definitions of Acid/Base Arrhenius/Ostwald Brønsted/Lowry Lux/Flood ‘Solvent system’ Lewis Usanovich Arrhenius/Ostwald Acids and bases dissociate in H2O, + + releasing H (H3O ) and OH-. Arrhenius Ostwald + - H2O H (aq) + OH (aq) + H (aq) is an acid - OH (aq) is a base Brønsted/Lowry Proton theory retained but the definition is now independent of solvent Brønsted Lowry An acid is a proton donor and a base is a proton acceptor. + - Other solvents are also NH4 + NH2 2NH3 capable of self-ionisation + - Proton HCl + NH3 [NH ] Cl transferred from 4 acid to base Donor acid Acceptor base Brønsted/Lowry Every acid has a conjugate base and every base has a conjugate acid HA + B- A- + HB The conjugate base of a weak acid is a strong base, and the conjugate base of a strong acid is a weak base.
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