Preview Theory and Problems for Chemistry Olympiad Challenging Concepts in Chemistry by Zhihan Nan (2019) Preview Theory and Problems for Chemistry Olympiad Challenging Concepts in Chemistry by Zhihan Nan (2019) Preview Theory and Problems for Chemistry Olympiad Challenging Concepts in Chemistry by Zhihan Nan (2019) Preview Theory and Problems for Chemistry Olympiad Challenging Concepts in Chemistry by Zhihan Nan (2019)
10960_9789813238992_TP.indd 8/7/19 10:12 AM Other Related Titles from World Scientific Sequences and Mathematical Induction: In Mathematical Olympiad and Competitions Second Edition by Zhigang Feng translated by Feng Ma and Youren Wang ISBN: 978-981-121-103-4 ISBN: 978-981-121-207-9 (pbk) Algebraic Inequalities: In Mathematical Olympiad and Competitions by Ji Chen and Chaocheng Ji translated by Chaocheng Ji, Huyue Shen and Ruhe Wang ISBN: 978-1-938134-95-1 ISBN: 978-1-938134-92-0 (pbk) Geometric Inequalities: In Mathematical Olympiad and Competitions by Gangsong Leng translated by Yongming Liu ISBN: 978-981-4704-13-7 ISBN: 978-981-4696-48-7 (pbk) A Central European Olympiad: The Mathematical Duel by Robert Geretschläger, Józef Kalinowski and Jaroslav Švrček ISBN: 978-981-3226-16-6 ISBN: 978-981-3223-90-5 (pbk) Combinatorial Extremization: In Mathematical Olympiad and Competitions by Yuefeng Feng ISBN: 978-981-4730-02-0 ISBN: 978-981-4723-16-9 (pbk) Physics Olympiad — Basic to Advanced Exercises by The Committee of Japan Physics Olympiad ISBN: 978-981-4556-67-5 (pbk) JQuek - 10960 - Theory and Problems for Chemistry Olympiad.indd 16-10-19 10:59:22 AM 10960_9789813238992_TP.indd 8/7/19 10:12 AM Published by World Scientific Publishing Co Pte Ltd Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE Library of Congress Cataloging-in-Publication Data Names: Nan, Zhihan, author | Zhang, Sheng (Lecturer in chemistry), author Title: Theory and problems for Chemistry Olympiad : challenging concepts in chemistry / Zhihan Nan, Sheng Zhang Description: New Jersey : World Scientific, [2020] | Includes index Identifiers: LCCN 2019030146 | ISBN 9789813238992 (hardcover) | ISBN 9789811210419 (paperback) Subjects: LCSH: International Chemistry Olympiad Study guides | Chemistry Problems, exercises, etc Classification: LCC QD42 N32 2019 | DDC 540.76 dc23 LC record available at https://lccn.loc.gov/2019030146 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Copyright © 2020 by World Scientific Publishing Co Pte Ltd All rights reserved This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the publisher For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA In this case permission to photocopy is not required from the publisher For any available supplementary material, please visit https://www.worldscientific.com/worldscibooks/10.1142/10960#t=suppl Typeset by Stallion Press Email: enquiries@stallionpress.com Printed in Singapore JQuek - 10960 - Theory and Problems for Chemistry Olympiad.indd 16-10-19 10:59:22 AM CONTENTS Foreword by Professor Richard Wong vii Attributions ix Introduction and General Tips to Prepare for Chemistry Olympiad Physical Chemistry 2.1 Thermodynamics 2.2 Chemical Equilibria 39 2.3 Thermodynamics of Phase Transitions 61 2.4 Thermodynamics of Mixtures 70 2.5 Electrochemistry 90 2.6 Reaction Kinetics 101 Inorganic Chemistry 121 3.1 Atomic Structure and Quantum Theory 122 3.2 Periodicity 134 3.3 Chemical Bonding 137 3.4 Acid-Base Chemistry 149 3.5 Main Group Chemistry 153 3.6 Crystal Structure 184 3.7 Coordination Chemistry 197 Organic Chemistry 225 4.1 Introduction to Organic Chemistry 226 4.2 Optical Activity and Stereochemistry 236 4.3 Conjugation and Aromaticity 245 b3585_ChemOlympiad.indb 24-Oct-19 10:32:50 AM vi Theory and Problems for Chemistry Olympiad 4.4 Acidity, Basicity, Nucleophilicity and Electrophilicity of Organic Compounds 252 4.5 Radical Chemistry 263 4.6 Nucleophilic Addition 277 4.7 Nucleophilic Substitution 289 4.8 Elimination Reactions 314 4.9 Electrophilic Addition 326 4.10 Electrophilic Substitution 336 4.11 Enolate Chemistry 350 4.12 Oxidation and Reduction 368 4.13 Protecting Groups in Organic Chemistry 381 4.14 Pericyclic Reactions 386 4.15 Organometallic Chemistry 400 4.16 Retrosynthetic Analysis 408 Practical Techniques 416 5.1 Titration 417 5.2 Techniques in Organic Synthesis 425 5.3 Qualitative Analysis 430 Sample Problems and Solutions 444 6.1 Sample Problem Set 447 6.2 Solutions to the Sample Problems 464 Index b3585_ChemOlympiad.indb 539 24-Oct-19 10:32:50 AM FOREWORD The International Chemistry Olympiad (IChO) celebrated its 50 th anniversary in 2018, growing from a small competition with only participating countries and 18 competing students to what it is now — a worldwide event attracting 76 countries and 300 students To select a team of students to represent Singapore at IChO, the Singapore Chemistry Olympiad (SChO) was launched in 1989 and it has become an annual event since then Chemistry Olympiad aims to motivate pre-tertiary students to study beyond the syllabus and stimulate their thinking through solving challenging chemistry problems It is able to further develop the interest of pre-tertiary students in chemistry and improve chemistry education by providing interested students with more resources This book is the first textbook that caters specifically to students preparing for the Chemistry Olympiad competition Previously, eager students had to browse through many university level textbooks to gain bits and pieces of information in the different fields of chemistry The objective of this book is to bring down university level concepts to pre-tertiary students in a concise manner, combining important knowledge from all fields of chemistry into one book The book presents chemical concepts in a succinct fashion, with key focus on the logical flow of concepts Clear explanations are given such that students are able to fully understand the theories presented As I read through the draft of “Theories and Problems for Chemistry Olympiad”, I was impressed by how the concepts taught in university are linked to the topics familiar to pre-tertiary students The knowledge gap was bridged through detailed justification, with every physical chemistry equation derived and every organic reaction described by its mechanism It was a joy to read through as there were many figures and diagrams used to illustrate the concepts The writing is clear and easy to read, so it should help even a beginner get his/her bearing In particular, the pedagogy is effective in keeping readers engaged as each chapter connects to the next At the end of the book, students are also able to test their understanding by attempting sample IChO problems with detailed solutions b3585_ChemOlympiad.indb 24-Oct-19 10:32:50 AM viii Theory and Problems for Chemistry Olympiad Nan Zhihan has participated in IChO 2016, achieving a gold medal and the IUPAC prize for highest score in the experimental examination After participating in the competition, he has devoted much of his efforts in mentoring and training the Singapore team for IChO 2017, 2018 and 2019 As a gold medallist, he understands the requirements and challenges in preparing for the competition and shares his personal experience in this book Dr Zhang Sheng is a lecturer at the Department of Chemistry, NUS, and has been the mentor of the Singapore Chemistry Olympiad team for years, training and leading the Singapore team for International Chemistry Olympiad competitions Over the years of his mentorship, Singapore team has won a total of 16 Gold Medals and 19 Silver Medals in IChO With vast experience in Chemistry Olympiad training, Nan Zhihan and Zhang Sheng form a formidable team to complete this valuable resource for perspective students I believe that this book is a valuable companion for students preparing for the Chemistry Olympiad competition However, I would also recommend this book to any student curious to learn more about chemistry, including freshmen at university With Chemistry Olympiad gaining prominence, I encourage interested students to take up the challenge and discover their passion in chemistry Professor Wong Ming Wah, Richard Head, Department of Chemistry National University of Singapore b3585_ChemOlympiad.indb 24-Oct-19 10:32:50 AM ATTRIBUTIONS Chapter 2.5 Figure 2.5.4: Sample galvanic cell by Hazmat2 is from Wikipedia commons Chapter 3.1 Figures 3.1.2 to 3.1.4 and 3.1.6: Orbital Graphs by As6673 are from Wikipedia commons, licensed under CC BY-SA 3.0 Chapter 3.6 Figure 3.6.2: Monoclinic cell by Fred the Oyster from Wikipedia commons, licensed under CC BY-SA 3.0 Modified to describe the crystal systems Figure 3.6.3: Primitive cubic unit cell by DaniFeri from Wikipedia commons, licensed under CC BY-SA 3.0 Figure 3.6.4 and Figure 3.6.7: Body-centred cubic unit cell by Chris He from Wikipedia commons, licensed under CC BY-SA 4.0 Each figure has been modified to show only unit cell Atom labels are added for CsCl unit cell Figure 3.6.5: Face-centred cubic unit cell by Christophe Dang Ngoc Chan from Wikipedia commons, licensed under CC BY-SA 3.0 Modified to show only unit cell Figure 3.6.6: NaCl lattice by Prolineserver from Wikipedia commons, licensed under CC BY-SA 3.0 Atom labels were added to the lattice Figure 3.6.8 and Figure 3.6.9: Fluorite and Zinc Blende crystal structure by Tem5psu from Wikipedia commons, licensed under CC BY-SA 4.0 Each figure has been modified to show only unit cell Atoms are labelled for both crystal structures Figure 3.6.11: Spinel unit cell by Andif1 from Wikipedia commons, licensed under CC BY-SA 4.0 Atoms are labelled on the figure Figures 3.6.12 to 3.6.14: Figures for the types of crystal defects by VladVB from Wikipedia commons, licensed under CC BY-SA 3.0 b3585_ChemOlympiad.indb 24-Oct-19 10:32:50 AM This page intentionally left blank b3585_ChemOlympiad.indb 10 24-Oct-19 10:32:51 AM INTRODUCTION AND GENERAL TIPS TO PREPARE FOR CHEMISTRY OLYMPIAD Welcome to Chemistry Olympiad! Chemistry Olympiad is a challenging competition that tests students on their higher-order thinking ability and encourages interested high school students to read up beyond the syllabus This book was written to explain tough university chemistry concepts to high school students, by building up the student’s knowledge slowly starting from the basics When reading this book, please appreciate the logical flow of concepts and find the links between different topics With time, I hope that you will see the beauty in chemistry, and have an enriching journey through Chemistry Olympiad b3585_ChemOlympiad.indb 24-Oct-19 10:32:51 AM 2 Theory and Problems for Chemistry Olympiad As the flow of chapters and content in this book is meticulously designed, I would urge you to read the book following the order of the chapters and sub-chapters This will ensure that you have the proper background knowledge required to understand every chapter fully After completing the book once, it can be used as a reference book to refresh yourself on the relevant topics once in a while As a tip, it will be good to keep a notebook to write down important concepts and equations while reading the book From the derivations of equations in physical chemistry to the mechanisms in organic chemistry, it is important to try these on your own to fully understand the concepts While looking at complicated reactions or concepts, keep questioning in your head why each step proceeds the way it does Note down any questions you have and ask your supervisor While the learning curve is definitely steep, I am sure that the rewards are worth every bit of time and effort The journey through Chemistry Olympiad is most rewarding when you are driven by your interest in chemistry and curiosity to learn more, instead of just going for a medal in the competition In Chemistry Olympiad, the competition is the final challenge to test your ability In most countries, there are various national Olympiad competitions to select students for the International Chemistry Olympiad (IChO), the dream for most aspiring Chemistry Olympians After all the hard work that is put into learning chemistry, it is critical to perform to the best of your ability at the competition Here, the authors list some tips from experience to help students their best at the competition For any competition, stress and mood through the examination play a significant role in how well we can think When years of hard work culminate in a 5-hour long examination, it is difficult to not be overwhelmed by stress Thus, you should face every competition with excitement, thinking of the competition as a new opportunity to learn more chemistry through problem-solving Even if you are unsure of the solution to certain problems, not let it discourage you, as the Olympiad competition is designed to be challenging In the end, it is not the results that matter the most, but that you have given your best effort through the journey of learning chemistry Upon starting the paper, browse through all the questions first Generally, Olympiad questions are not ranked by difficulty level In particular, while one student may find an organic chemistry question more challenging, another student may have a difficult time solving a physical chemistry question In the Olympiad competition, many students will find themselves having insufficient time to complete all the questions Thus, find the questions that you are most confident in solving, and ensure that they are completed correctly and efficiently before attempting the more challenging problems For some common constants, you should use the value that is given in the “Constants and Formulae” table in front of the paper, regardless whether the value is the same or different compared to the value you have memorised For example, the b3585_ChemOlympiad.indb 24-Oct-19 10:32:51 AM Introduction and General Tips to Prepare for Chemistry Olympiad speed of light is given as c = 3.000 × 108 m ⋅ s-1 (IChO 2011) and c = 2.998 × 108 m ⋅ s-1 (IChO 2018) You should also use the atomic mass from the Periodic Table given in the question paper For example, the mass of a hydrogen atom was given as 1.01 (IChO 2010), 1.008 (IChO 2011) and 1.00794 (IChO 2015) For physical chemistry questions, it is important to show full workings on how the answer was obtained Sometimes, there might be small errors during the calculation that lead to a different answer If the final answer is incorrect, points may be awarded for correct equations in the working To avoid losing all the points due to a small careless error, please show all key steps leading to the final answer This also helps when checking the answer again for any errors While working through physical chemistry problems, it is recommended to leave your answers in symbolic form while working through the problem This makes it easier to spot any algebraic errors, and minimise the time spent on pressing the calculator If any intermediate value is obtained, try to leave it to or more significant figures than the final required answer You not need to copy down all the decimal places from your calculator, because that’s just a waste of your time and it will not affect your final results As per all scientific calculations, standard rules for decimal places and significant figures apply in Chemistry Olympiad calculation If a question requires students to report the results to a certain number of significant figures, such requirement should be stated clearly in the question If a question has not stated such a requirement, then you just need to report your value with a reasonable number of significant figures For example, a concentration of 0.1028 mol ⋅ dm -3 or 0.103 mol ⋅ dm -3 is reasonable, but 0.102774125 mol ⋅ dm -3 is obviously not reasonable although that’s the value shown on the calculator For inorganic chemistry, it is important to be familiar with the properties of different elements and ions, such as the colour of transition metal cations in their various oxidation states, the flame test results of cations, common oxidation states of elements, solubility of common inorganic salts and colour of common precipitates This information will often give intuition into the identity of unknown compounds in inorganic elucidation questions While a summary is provided in the qualitative analysis Table 5.1, I would still encourage students to test out reactions and make the observations themselves You should also memorise the atomic mass of common elements, as this will allow you to easily access molecular masses of common compounds This may be useful to deduce the identity of inorganic compounds in calculation-type questions For example, a molecular mass of 18 suggests H2O, 28 suggests CO, and 44 suggests CO2 Now, try the following for yourself: 98, 100, 160 Of course, there are still many others You should try to summarise your own table of common molecules and their molecular masses Other than deducing compound identity through calculations, it is also possible to make good judgements based on periodicity and the trends within each group b3585_ChemOlympiad.indb 24-Oct-19 10:32:51 AM 4 Theory and Problems for Chemistry Olympiad Thus, it is good to have a brief understanding of the elemental trends in each group, as outlined in chapter 3.5 For organic chemistry, it is useful to work on structural elucidation both forwards and backwards The process of visualising a synthesis backwards is known as retro synthesis, and is briefly discussed in chapter 4.16 You can compare the reactant and product to determine the parts of the molecule with no change After identifying the parts that not change in the reaction, it is possible to focus on the reactive site(s) This allows us to deduce the reaction mechanism, which may be single or multi-step From time to time, you will encounter some organic reagents that you have not met before Based on structural features, it is possible to compare such reagents with familiar reagents to deduce its role, as solvent, catalyst, acid, base, oxidant, reductant, nucleophile or electrophile Once its role is confirmed, it is possible to determine the reaction mechanism and predict the product When analysing reactions, pay special attention to selectivity, including chemoselectivity, regioselectivity and stereoselectivity In particular, stereoselectivity is often encountered in Chemistry Olympiad Sometimes, stereochemistry can be deduced either from the reactant one or several steps before, or from the product one or several steps after Also, you should decide whether there is a retention or inversion of stereochemistry based on the reaction mechanism In general, stereochemistry should be shown clearly with wedged or dotted lines The tips provided here in this chapter are general and more specific tips regarding each topic will be given as you move on into the book I wish all students an enriching and rewarding Chemistry Olympiad journey! b3585_ChemOlympiad.indb 24-Oct-19 10:32:51 AM ... Cataloging -in- Publication Data Names: Nan, Zhihan, author | Zhang, Sheng (Lecturer in chemistry) , author Title: Theory and problems for Chemistry Olympiad : challenging concepts in chemistry / Zhihan. .. understanding by attempting sample IChO problems with detailed solutions b3585_ChemOlympiad.indb 24-Oct-19 10:32:50 AM viii Theory and Problems for Chemistry Olympiad Nan Zhihan has participated in. .. their thinking through solving challenging chemistry problems It is able to further develop the interest of pre-tertiary students in chemistry and improve chemistry education by providing interested