Chapter 16 Acid-Base Equilibria
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Wastewater Technology Fact Sheet: Ammonia Stripping
United States Office of Water EPA 832-F-00-019 Environmental Protection Washington, D.C. September 2000 Agency Wastewater Technology Fact Sheet Ammonia Stripping DESCRIPTION Ammonia stripping is a simple desorption process used to lower the ammonia content of a wastewater stream. Some wastewaters contain large amounts of ammonia and/or nitrogen-containing compounds that may readily form ammonia. It is often easier and less expensive to remove nitrogen from wastewater in the form of ammonia than to convert it to nitrate-nitrogen before removing it (Culp et al., 1978). Ammonia (a weak base) reacts with water (a weak acid) to form ammonium hydroxide. In ammonia stripping, lime or caustic is added to the wastewater until the pH reaches 10.8 to 11.5 standard units which converts ammonium hydroxide ions to ammonia gas according to the following reaction(s): + - NH4 + OH 6 H2O + NH38 Source: Culp, et. al, 1978. Figure 1 illustrates two variations of ammonia FIGURE 1 TWO TYPES OF STRIPPING stripping towers, cross-flow and countercurrent. In TOWERS a cross-flow tower, the solvent gas (air) enters along the entire depth of fill and flows through the packing, as the alkaline wastewater flows it may be more economical to use alternate downward. A countercurrent tower draws air ammonia removal techniques, such as steam through openings at the bottom, as wastewater is stripping or biological methods. Air stripping may pumped to the top of a packed tower. Free also be used to remove many hydrophobic organic ammonia (NH3) is stripped from falling water molecules (Nutrient Control, 1983). droplets into the air stream, then discharged to the atmosphere. -
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). -
The Strongest Acid Christopher A
Chemistry in New Zealand October 2011 The Strongest Acid Christopher A. Reed Department of Chemistry, University of California, Riverside, California 92521, USA Article (e-mail: [email protected]) About the Author Chris Reed was born a kiwi to English parents in Auckland in 1947. He attended Dilworth School from 1956 to 1964 where his interest in chemistry was un- doubtedly stimulated by being entrusted with a key to the high school chemical stockroom. Nighttime experiments with white phosphorus led to the Headmaster administering six of the best. He obtained his BSc (1967), MSc (1st Class Hons., 1968) and PhD (1971) from The University of Auckland, doing thesis research on iridium organotransition metal chemistry with Professor Warren R. Roper FRS. This was followed by two years of postdoctoral study at Stanford Univer- sity with Professor James P. Collman working on picket fence porphyrin models for haemoglobin. In 1973 he joined the faculty of the University of Southern California, becoming Professor in 1979. After 25 years at USC, he moved to his present position of Distinguished Professor of Chemistry at UC-Riverside to build the Centre for s and p Block Chemistry. His present research interests focus on weakly coordinating anions, weakly coordinated ligands, acids, si- lylium ion chemistry, cationic catalysis and reactive cations across the periodic table. His earlier work included extensive studies in metalloporphyrin chemistry, models for dioxygen-binding copper proteins, spin-spin coupling phenomena including paramagnetic metal to ligand radical coupling, a Magnetochemi- cal alternative to the Spectrochemical Series, fullerene redox chemistry, fullerene-porphyrin supramolecular chemistry and metal-organic framework solids (MOFs). -
A Guide to Acids, Acid Strength, and Concentration
A GUIDE TO ACIDS, ACID STRENGTH, AND CONCENTRATION What’s the difference between acid strength and concentration? And how does pH fit in with these? This graphic explains the basics. CH COOH HCl H2SO4 HNO3 H3PO4 HF 3 H2CO3 HYDROCHLORIC ACID SULFURIC ACID NITRIC ACID PHOSPHORIC ACID HYDROFLUORIC ACID ETHANOIC ACID CARBONIC ACID pKa = –7 pKa = –2 pKa = –2 pKa = 2.12 pKa = 3.45 pKa = 4.76 pKa = 6.37 STRONGER ACIDS WEAKER ACIDS STRONG ACIDS VS. WEAK ACIDS ACIDS, Ka AND pKa CONCENTRATION AND pH + – The H+ ion is transferred to a + A decrease of one on the pH scale represents + [H+] [A–] pH = –log10[H ] a tenfold increase in H+ concentration. HA H + A water molecule, forming H3O Ka = pKa = –log10[Ka] – [HA] – – + + A + + A– + A + A H + H H H H A H + H H H A Ka pK H – + – H a A H A A – + A– A + H A– H A– VERY STRONG ACID >0.1 <1 A– + H A + + + – H H A H A H H H + A – + – H A– A H A A– –3 FAIRLY STRONG ACID 10 –0.1 1–3 – – + A A + H – – + – H + H A A H A A A H H + A A– + H A– H H WEAK ACID 10–5–10–3 3–5 STRONG ACID WEAK ACID VERY WEAK ACID 10–15–10–5 5–15 CONCENTRATED ACID DILUTE ACID + – H Hydrogen ions A Negative ions H A Acid molecules EXTREMELY WEAK ACID <10–15 >15 H+ Hydrogen ions A– Negative ions Acids react with water when they are added to it, The acid dissociation constant, Ka, is a measure of the Concentration is distinct from strength. -
Properties of Acids and Bases
GREEN CHEMISTRY LABORATORY MANUAL Lab 22 Properties of Acids and Bases TN Standard 4.2: The student will investigate the characteristics of acids and bases. Have you ever brushed your teeth and then drank a glass of orange juice? hat do you taste when you brush your teeth and drink orange juice afterwards. Yuck! It leaves a really bad taste in your mouth, but why? Orange juice and toothpaste by themselves taste good. But the terrible taste W results because an acid/base reaction is going on in your mouth. Orange juice is a weak acid and the toothpaste is a weak base. When they are placed together they neutralize each other and produce a product that is unpleasant to taste. How do you determine what is an acid and what is a base? In this lab we will discover how to distinguish between acids and bases. Introduction Two very important classes of compounds are acids and bases. But what exactly makes them different? There are differences in definition, physical differences, and reaction differences. According to the Arrhenius definition, acids ionize in water to + produce a hydronium ion (H3O ), and bases dissociate in water to produce hydroxide ion (OH -). Physical differences can be detected by the senses, including taste and touch. Acids have a sour or tart taste and can produce a stinging sensation to broken skin. For example, if you have ever tasted a lemon, it can often result in a sour face. Bases have a bitter taste and a slippery feel. Soap and many cleaning products are bases. -
Answer Key Chapter 16: Standard Review Worksheet – + 1
Answer Key Chapter 16: Standard Review Worksheet – + 1. H3PO4(aq) + H2O(l) H2PO4 (aq) + H3O (aq) + + NH4 (aq) + H2O(l) NH3(aq) + H3O (aq) 2. When we say that acetic acid is a weak acid, we can take either of two points of view. Usually we say that acetic acid is a weak acid because it doesn’t ionize very much when dissolved in water. We say that not very many acetic acid molecules dissociate. However, we can describe this situation from another point of view. We could say that the reason acetic acid doesn’t dissociate much when we dissolve it in water is because the acetate ion (the conjugate base of acetic acid) is extremely effective at holding onto protons and specifically is better at holding onto protons than water is in attracting them. + – HC2H3O2 + H2O H3O + C2H3O2 Now what would happen if we had a source of free acetate ions (for example, sodium acetate) and placed them into water? Since acetate ion is better at attracting protons than is water, the acetate ions would pull protons out of water molecules, leaving hydroxide ions. That is, – – C2H3O2 + H2O HC2H3O2 + OH Since an increase in hydroxide ion concentration would take place in the solution, the solution would be basic. Because acetic acid is a weak acid, the acetate ion is a base in aqueous solution. – – 3. Since HCl, HNO3, and HClO4 are all strong acids, we know that their anions (Cl , NO3 , – and ClO4 ) must be very weak bases and that solutions of the sodium salts of these anions would not be basic. -
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. -
Multidisciplinary Design Project Engineering Dictionary Version 0.0.2
Multidisciplinary Design Project Engineering Dictionary Version 0.0.2 February 15, 2006 . DRAFT Cambridge-MIT Institute Multidisciplinary Design Project This Dictionary/Glossary of Engineering terms has been compiled to compliment the work developed as part of the Multi-disciplinary Design Project (MDP), which is a programme to develop teaching material and kits to aid the running of mechtronics projects in Universities and Schools. The project is being carried out with support from the Cambridge-MIT Institute undergraduate teaching programe. For more information about the project please visit the MDP website at http://www-mdp.eng.cam.ac.uk or contact Dr. Peter Long Prof. Alex Slocum Cambridge University Engineering Department Massachusetts Institute of Technology Trumpington Street, 77 Massachusetts Ave. Cambridge. Cambridge MA 02139-4307 CB2 1PZ. USA e-mail: [email protected] e-mail: [email protected] tel: +44 (0) 1223 332779 tel: +1 617 253 0012 For information about the CMI initiative please see Cambridge-MIT Institute website :- http://www.cambridge-mit.org CMI CMI, University of Cambridge Massachusetts Institute of Technology 10 Miller’s Yard, 77 Massachusetts Ave. Mill Lane, Cambridge MA 02139-4307 Cambridge. CB2 1RQ. USA tel: +44 (0) 1223 327207 tel. +1 617 253 7732 fax: +44 (0) 1223 765891 fax. +1 617 258 8539 . DRAFT 2 CMI-MDP Programme 1 Introduction This dictionary/glossary has not been developed as a definative work but as a useful reference book for engi- neering students to search when looking for the meaning of a word/phrase. It has been compiled from a number of existing glossaries together with a number of local additions. -
Drugs and Acid Dissociation Constants Ionisation of Drug Molecules Most Drugs Ionise in Aqueous Solution.1 They Are Weak Acids Or Weak Bases
Drugs and acid dissociation constants Ionisation of drug molecules Most drugs ionise in aqueous solution.1 They are weak acids or weak bases. Those that are weak acids ionise in water to give acidic solutions while those that are weak bases ionise to give basic solutions. Drug molecules that are weak acids Drug molecules that are weak bases where, HA = acid (the drug molecule) where, B = base (the drug molecule) H2O = base H2O = acid A− = conjugate base (the drug anion) OH− = conjugate base (the drug anion) + + H3O = conjugate acid BH = conjugate acid Acid dissociation constant, Ka For a drug molecule that is a weak acid The equilibrium constant for this ionisation is given by the equation + − where [H3O ], [A ], [HA] and [H2O] are the concentrations at equilibrium. In a dilute solution the concentration of water is to all intents and purposes constant. So the equation is simplified to: where Ka is the acid dissociation constant for the weak acid + + Also, H3O is often written simply as H and the equation for Ka is usually written as: Values for Ka are extremely small and, therefore, pKa values are given (similar to the reason pH is used rather than [H+]. The relationship between pKa and pH is given by the Henderson–Hasselbalch equation: or This relationship is important when determining pKa values from pH measurements. Base dissociation constant, Kb For a drug molecule that is a weak base: 1 Ionisation of drug molecules. 1 Following the same logic as for deriving Ka, base dissociation constant, Kb, is given by: and Ionisation of water Water ionises very slightly. -
Chapter 12 "Acids and Bases"
This is “Acids and Bases”, chapter 12 from the book Beginning Chemistry (index.html) (v. 1.0). This book is licensed under a Creative Commons by-nc-sa 3.0 (http://creativecommons.org/licenses/by-nc-sa/ 3.0/) license. See the license for more details, but that basically means you can share this book as long as you credit the author (but see below), don't make money from it, and do make it available to everyone else under the same terms. This content was accessible as of December 29, 2012, and it was downloaded then by Andy Schmitz (http://lardbucket.org) in an effort to preserve the availability of this book. Normally, the author and publisher would be credited here. However, the publisher has asked for the customary Creative Commons attribution to the original publisher, authors, title, and book URI to be removed. Additionally, per the publisher's request, their name has been removed in some passages. More information is available on this project's attribution page (http://2012books.lardbucket.org/attribution.html?utm_source=header). For more information on the source of this book, or why it is available for free, please see the project's home page (http://2012books.lardbucket.org/). You can browse or download additional books there. i 635 Chapter 12 Acids and Bases Chapter 12 Acids and Bases 636 Chapter 12 Acids and Bases Opening Essay Formerly there were rather campy science-fiction television shows in which the hero was always being threatened with death by being plunged into a vat of boiling acid: “Mwa ha ha, Buck Rogers [or whatever the hero’s name was], prepare to meet your doom by being dropped into a vat of boiling acid!” (The hero always escapes, of course.) This may have been interesting drama but not very good chemistry.