Acids, Bases and Solution Equilibria
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Choosing Buffers Based on Pka in Many Experiments, We Need a Buffer That Maintains the Solution at a Specific Ph. We May Need An
Choosing buffers based on pKa In many experiments, we need a buffer that maintains the solution at a specific pH. We may need an acidic or a basic buffer, depending on the experiment. The Henderson-Hasselbalch equation can help us choose a buffer that has the pH we want. pH = pKa + log([conj. base]/[conj. acid]) With equal amounts of conjugate acid and base (preferred so buffers can resist base and acid equally), then … pH = pKa + log(1) = pKa + 0 = pKa So choose conjugates with a pKa closest to our target pH. Chemistry 103 Spring 2011 Example: You need a buffer with pH of 7.80. Which conjugate acid-base pair should you use, and what is the molar ratio of its components? 2 Chemistry 103 Spring 2011 Practice: Choose the best conjugate acid-base pair for preparing a buffer with pH 5.00. What is the molar ratio of the buffer components? 3 Chemistry 103 Spring 2011 buffer capacity: the amount of strong acid or strong base that can be added to a buffer without changing its pH by more than 1 unit; essentially the number of moles of strong acid or strong base that uses up all of the buffer’s conjugate base or conjugate acid. Example: What is the capacity of the buffer solution prepared with 0.15 mol lactic acid -4 CH3CHOHCOOH (HA, Ka = 1.0 x 10 ) and 0.20 mol sodium lactate NaCH3CHOHCOO (NaA) and enough water to make 1.00 L of solution? (from previous lecture notes) 4 Chemistry 103 Spring 2011 Review of equivalence point equivalence point: moles of H+ = moles of OH- (moles of acid = moles of base, only when the acid has only one acidic proton and the base has only one hydroxide ion). -
Oxygen Reduction Reactions in Ionic Liquids and the Formulation of a General ORR Mechanism for Li−Air Batteries † † † † ‡ Chris J
Article pubs.acs.org/JPCC Oxygen Reduction Reactions in Ionic Liquids and the Formulation of a General ORR Mechanism for Li−Air Batteries † † † † ‡ Chris J. Allen, Jaehee Hwang, Roger Kautz, Sanjeev Mukerjee, Edward J. Plichta, ‡ † Mary A. Hendrickson, and K. M. Abraham*, † Department of Chemistry and Chemical Biology, Northeastern University Center for Renewable Energy Technology (NUCRET), Northeastern University, Boston, Massachusetts 02115, United States ‡ Power Division, U.S. Army RDECOM CERDEC CP&I, RDER-CCP, 5100 Magazine Road, Aberdeen Proving Ground, Maryland 21005, United States ABSTRACT: Oxygen reduction and evolution reactions (ORRs and OERs) have been studied in ionic liquids containing singly charged cations having a range of ionic radii, or charge densities. Specifically, ORR and OER mechanisms were studied using cyclic and rotating disk electrode voltammetry in the neat ionic liquids (ILs), 1-ethyl- 3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI) and 1-methyl-1-butyl-pyrrolidinium bis- fl (tri ouromethanesulfonyl)imide (PYR14TFSI), and in their solutions containing LiTFSI, NaPF6, KPF6, and tetrabutylam- fl monium hexa uorophosphate (TBAPF6). A strong correlation was found between the ORR products and the ionic charge density, including those of the ionic liquids. The observed trend is explained in terms of the Lewis acidity of the cation present in the electrolyte using an acidity scale created from 13C − 13 NMR chemical shifts and spin lattice relaxation (T1) times of C O in solutions of these charged ions in propylene carbonate (PC). The ionic liquids lie in a continuum of a cascading Lewis acidity scale with respect to the charge density of alkali metal, IL, and TBA cations with the result that the ORR products in ionic liquids and in organic electrolytes containing any conducting cations can be predicted on the basis of a general theory based on the hard soft acid base (HSAB) concept. -
Acid-Base Interactions in Wetting
J. rldlresiortSci. Tetltttol. \irl. -5.No. l. pp.57-69 ( l99l ) o VsP t9el. Acid-baseinteractions in wetting GEORGE M. WHITESIDES,*HANS A. BIEBUYCK.JOHN P.FOLKERS andKEVIN L. PRIME Departntent of Chentistry,Harvard Universiry',Cambridge, hlA 02138,USA Revisedversion received 27 Aueust1990 Abstract-The studv of the ionizationof carboxylicacid groups at the interfacebetween organic solidsand water demonstratesbroad similaritiesto the ionizationsof thesegroups in homogeneous aqueoussolution, but with importantsystematic differences. Creation of a chargedgroup from a neutralone by protonationor deprotonation(whether -NHr* from -NH, or -CO; from -CO,H) at the interfacebetu'een surface-functionalized polyethylene and \r'ateris more difficult than that in homogeneousaqueous solution. This differenceis probably related to the low effectivedielectric constantof the interface(5=9) relativeto water (e=80). It is not known to what extentthis differencein e (and in other propertiesof the interphase,considered as a thin solventphase) is reflectedin the stabilityof the organicions relativeto their neutral forms in the interphaseand in - solution,and to whatextent in differencesin the concentrationof H' and OH in the interphaseand in solution.Self-assembled monolayers (SAMs)-especially of terminallyfunctionalized alkanethiols (HS(CH:),,X) adsorbedon gold-provide model systemswith relativelywell-ordered structures thar are useful in establishingthe fundamentalsof ionizationof protic acidsand basesat the interface betr"'eenorganic solids and water.These systems,coupled r.r'ithnew analyticalmethods such as photoacousticcalorimetry (PAC) and contact angletitration, may make it possibleto disentangle some of the complex puzzlespresented by proton-transferreactions in the environmentof the organicsolid-* ater interphase. Keyx'ords:Contact ansle titration; photoacoustic calorimetrv: poly'ethylene carboxylic acid: contact angle:polvmer surfaces; u'etting; self-assembled monolavers. -
Hydride Abstraction and Deprotonation – an Efficient Route to Low Co-Ordinate Phosphorus and Arsenic Species
Hydride Abstraction and Deprotonation – an Efficient Route to Low Co-ordinate Phosphorus and Arsenic Species Laurence J. Taylor, Michael Bühl, Piotr Wawrzyniak, Brian A. Chalmers, J. Derek Woollins, Alexandra M. Z. Slawin, Amy L. Fuller and Petr Kilian* School of Chemistry, EastCHEM, University of St Andrews, St Andrews, Fife, KY16 9ST, UK E-mail: [email protected] URL: http://chemistry.st-andrews.ac.uk/staff/pk/group/ Supporting information for this article is given via a link at the end of the document. Abstract Treatment of Acenap(PiPr2)(EH2) (Acenap = acenaphthene-5,6-diyl; 1a, E = As; 1b, E = P) with Ph3C·BF4 resulted in hydride abstraction to give [Acenap(PiPr2)(EH)][BF4] (2a, E = As; 2b, E = P). These represent the first structurally characterised phosphino/arsino-phosphonium salts with secondary arsine/phosphine groups, as well as the first example of a Lewis base stabilised primary arsenium cation. Compounds 2a and 2b were deprotonated with NaH to afford low co-ordinate species Acenap(PiPr2)(E) (3a, E = As; 3b, E = P). This provides an alternative and practical synthetic pathway to the phosphanylidene-σ4-phosphorane 3b and provides mechanistic insight into the formation of arsanylidene-σ4-phosphorane 3a, indirectly supporting the hypothesis that the previously reported dehydrogenation of 1a occurs via an ionic mechanism. Introduction 4 Alkylidene-σ -phosphoranes (R2C=PR3), more commonly known as Wittig reagents, are widely used intermediates in the formation of C=C double bonds. The arsenic and phosphorus equivalents, 4 4 arsanylidene-σ -phosphoranes (RAs=PR3) and phosphanylidene-σ -phosphoranes (RP=PR3), are rare 4 by comparison. -
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. -
Superacid Chemistry
SUPERACID CHEMISTRY SECOND EDITION George A. Olah G. K. Surya Prakash Arpad Molnar Jean Sommer SUPERACID CHEMISTRY SUPERACID CHEMISTRY SECOND EDITION George A. Olah G. K. Surya Prakash Arpad Molnar Jean Sommer Copyright # 2009 by John Wiley & Sons, Inc. All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission. Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. -
Soaps and Detergents • the Next Time You Are in a Supermarket, Go to the Aisle with Soaps and Detergents
23 Table of Contents 23 Unit 6: Interactions of Matter Chapter 23: Acids, Bases, and Salts 23.1: Acids and Bases 23.2: Strengths of Acids and Bases 23.3: Salts Acids and Bases 23.1 Acids • Although some acids can burn and are dangerous to handle, most acids in foods are safe to eat. • What acids have in common, however, is that they contain at least one hydrogen atom that can be removed when the acid is dissolved in water. Acids and Bases 23.1 Properties of Acids • An acid is a substance that produces hydrogen ions in a water solution. It is the ability to produce these ions that gives acids their characteristic properties. • When an acid dissolves in water, H+ ions + interact with water molecules to form H3O ions, which are called hydronium ions (hi DROH nee um I ahnz). Acids and Bases 23.1 Properties of Acids • Acids have several common properties. • All acids taste sour. • Taste never should be used to test for the presence of acids. • Acids are corrosive. Acids and Bases 23.1 Properties of Acids • Acids also react with indicators to produce predictable changes in color. • An indicator is an organic compound that changes color in acid and base. For example, the indicator litmus paper turns red in acid. Acids and Bases 23.1 Common Acids • At least four acids (sulfuric, phosphoric, nitric, and hydrochloric) play vital roles in industrial applications. • This lists the names and formulas of a few acids, their uses, and some properties. Acids and Bases 23.1 Bases • You don’t consume many bases. -
Introduction to Ionic Mechanisms Part I: Fundamentals of Bronsted-Lowry Acid-Base Chemistry
INTRODUCTION TO IONIC MECHANISMS PART I: FUNDAMENTALS OF BRONSTED-LOWRY ACID-BASE CHEMISTRY HYDROGEN ATOMS AND PROTONS IN ORGANIC MOLECULES - A hydrogen atom that has lost its only electron is sometimes referred to as a proton. That is because once the electron is lost, all that remains is the nucleus, which in the case of hydrogen consists of only one proton. The large majority of organic reactions, or transformations, involve breaking old bonds and forming new ones. If a covalent bond is broken heterolytically, the products are ions. In the following example, the bond between carbon and oxygen in the t-butyl alcohol molecule breaks to yield a carbocation and hydroxide ion. H3C CH3 H3C OH H3C + OH CH3 H3C A tertiary Hydroxide carbocation ion The full-headed curved arrow is being used to indicate the movement of an electron pair. In this case, the two electrons that make up the carbon-oxygen bond move towards the oxygen. The bond breaks, leaving the carbon with a positive charge, and the oxygen with a negative charge. In the absence of other factors, it is the difference in electronegativity between the two atoms that drives the direction of electron movement. When pushing arrows, remember that electrons move towards electronegative atoms, or towards areas of electron deficiency (positive, or partial positive charges). The electron pair moves towards the oxygen because it is the more electronegative of the two atoms. If we examine the outcome of heterolytic bond cleavage between oxygen and hydrogen, we see that, once again, oxygen takes the two electrons because it is the more electronegative atom. -
2701X0073.Pdf
COORDINATION AND REDOX PROPERTIES IN SOLUTION YIKTOR GUTMANN Inst it Ut für Anorganische Chemie der Technischen Hochschule Wien, Austria ABSTRACT A primitive description of the functional electron cloud is given and is used to account for the mutual influence between coordinating and redox properties. Rules are given for the change in redox properties by coordination and vice versa. It is further shown that the redox potential in a donor solvent is determined by its donor number and an empirical approach is suggested to obtain the electromotive series for any solvent of given donor number. The donor number is also considered important for the ionization of a covalent substrate. Finally a new classification is suggested for charge-transfer complexes. THE PRIMITIVE DESCRIPTION OF THE FUNCTIONAL ELECTRON CLOUD In a primitive way, a characteristic 'electron cloud' may be ascribed to each atom, ion or molecule. Even in the state of highest stability of the entity, the ground state, the electronic arrangement is usually far from 'ideal' as is evidenced by the tendency to undergo chemical reactions. In the primitive description of the 'functional electron cloud', the 'non-ideality' of the cloud is considered responsible for its tendency to change; the actual function will depend also on the properties of the reactant. The functional cloud may deviate from the ideal by being either too 'dilute' or too 'dense' compared with that of the reacting molecule. An entity with a 'dilute' electron cloud will tend to gain electrons or to achieve an appropriate share of them and will thus function as an acceptor of elec- trons. -
Ionic Equilibria in Donor Solvents
IONIC EQUILIBRIA IN DONOR SOLVENTS U. MAYER Technical University of Vienna, Department of Inorganic Chemistry, A-1060 Vienna, Austria ABSTRACT It is shown that coordination chemical and extrathermodynamic models may be successfully applied to the qualitative and also quantitative description of fundamental chemical equilibria and reaction rates in non-aqueous solvents. Applications include: formation of charge transfer complexes, electrochemical reduction of metal cations, ionization of covalent compounds, ion association phenomena, outer sphere interactions and the kinetics of substitution reactions. I. INTRODUCTION During recent decades rapid developments have taken place in the field of non-aqueous solution chemistry. This may be attributed to: first, the increased use of non-aqueous solvents as reaction media in preparative chemistry and in technological processes; and second, the ever-increasing importance of these solvents within the scope of physical chemical studies on the nature of solute—solvent interactions. The previous lack of efficient models for a generalized description of solute—solvent interactions was undoubtedly due to the fact that physical chemists concentrated their efforts for many years on aqueous solutions or at best on a few closely related solvent systems. Thus, only when scientists began to study suitable model reactions in a variety of non-aqueous media with widely different properties has it become possible to establish generalized relationships between chemical reactivity and solvent properties, to test critically existing theories, and to develop new and more efficient models. The main problem in solution chemistry is the characterization of ion— solvent interactions. It is well known that single ion solvation quantities cannot be determined by purely thermodynamic methods. -
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. -
Title a Hydronium Solvate Ionic Liquid
A Hydronium Solvate Ionic Liquid: Facile Synthesis of Air- Title Stable Ionic Liquid with Strong Bronsted Acidity Kitada, Atsushi; Takeoka, Shun; Kintsu, Kohei; Fukami, Author(s) Kazuhiro; Saimura, Masayuki; Nagata, Takashi; Katahira, Masato; Murase, Kuniaki Journal of the Electrochemical Society (2018), 165(3): H121- Citation H127 Issue Date 2018-02-22 URL http://hdl.handle.net/2433/240665 © The Author(s) 2018. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, Right http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. Type Journal Article Textversion publisher Kyoto University Journal of The Electrochemical Society, 165 (3) H121-H127 (2018) H121 A Hydronium Solvate Ionic Liquid: Facile Synthesis of Air-Stable Ionic Liquid with Strong Brønsted Acidity Atsushi Kitada, 1,z Shun Takeoka,1 Kohei Kintsu,1 Kazuhiro Fukami,1,∗ Masayuki Saimura,2 Takashi Nagata,2 Masato Katahira,2 and Kuniaki Murase1,∗ 1Department of Materials Science and Engineering, Kyoto University, Yoshida-honmachi, Sakyo, Kyoto 606-8501, Japan 2Institute of Advanced Energy, Gokasho, Uji, Kyoto 611-0011, Japan + A new kind of ionic liquid (IL) with strong Brønsted acidity, i.e., a hydronium (H3O ) solvate ionic liquid, is reported. The IL can + + be described as [H3O · 18C6]Tf2N, where water exists as the H3O ion solvated by 18-crown-6-ether (18C6), of which the counter – – + anion is bis(trifluoromethylsulfonyl)amide (Tf2N ;Tf= CF3SO2). The hydrophobic Tf2N anion makes [H3O · 18C6]Tf2N stable + in air.