chemistry for chemical engineers

Dr Ashleigh J Fletcher Chemistry for Chemical Engineers Download free eBooks at bookboon.com Chemistry for Chemical Engineers © 2012 Dr Ashleigh J Fletcher & bookboon.com ISBN 978-87-403-0249-3 Download free eBooks at bookboon.com Chemistry for Chemical Engineers Contents Contents Quantifying systems Atoms and bonding 11 he periodic table 20 Molecular structure 34 Mass and volume 39 he mole 42 Stoichiometry 44 Acid-base chemistry 46 Basic organic chemistry 54 Basic thermodynamics 67 www.sylvania.com We not reinvent the wheel we reinvent light Fascinating lighting offers an ininite spectrum of possibilities: Innovative technologies and new markets provide both opportunities and challenges An environment in which your expertise is in high demand Enjoy the supportive working atmosphere within our global group and beneit from international career paths Implement sustainable ideas in close cooperation with other specialists and contribute to inluencing our future Come and join us in reinventing light every day Light is OSRAM Download free eBooks at bookboon.com Click on the ad to read more Chemistry for Chemical Engineers Contents Kinetic theory of gases 73 Physical properties of gases 78 Equilibria and kinetics 82 Efect of reaction conditions on the equilibrium position 89 Liquids and solutions 91 Colligative properties 97 Chemical reactions 101 Hess’s law and temperature dependence of equilibria 105 Material balances 114 Energy balances 119 Biography for Dr Ashleigh Fletcher 125 360° thinking Discover the truth at www.deloitte.ca/careers Download free eBooks at bookboon.com © Deloitte & Touche LLP and affiliated entities Click on the ad to read more Chemistry for Chemical Engineers Two of the main distinctions between chemical engineers and other engineering disciplines are the topics of mass and energy balances Within these two topics there are a lot of underlying chemical principles that help chemical engineers to perform calculations to determine what is happening in a system, allowing better control of a process his book will outline the basic chemistry principles that are required by chemical engineers to understand chemical reactions and relate them to the main themes of mass and energy balances It does not serve as a complete account of all the chemistry that is important for chemical engineering but should give a grounding, which can be supplemented by reading further into the areas discussed, if required Download free eBooks at bookboon.com Chemistry for Chemical Engineers Quantifying systems Quantifying systems Working as a chemical engineer requires a capacity to interpret data and quantities provided from diferent sources It is essential that any quantities used or calculated are recorded correctly, as the inclusion or omission of units changes the context dramatically For example is a purely numerical quantity, but adding a unit, say kilograms so the measurement becomes kg, conveys signiicantly more information In all working it is important to write down both numerical values and the corresponding units; as a result, it is necessary to appreciate the relationship between certain units and have an ability to convert between quantities he properties that can be measured, such as time, length and mass, are known as dimensions and can also be composed from multiplying or dividing other dimensions, for example velocity (length/ time) Units can be treated like algebraic variables when quantities are added, subtracted, multiplied or divided but note that numerical values may only be added or subtracted if their units are the same he most common set of units that chemical engineers come into contact with are the seven fundamental S.I units of measurement, as deined in the International System of Units (the abbreviation S.I comes from the French for this classiication: Système Internationale d’Unités) he system was developed in 1960 and has been widely accepted by the science and engineering communities he table below shows the seven base units and their corresponding abbreviations, as chemical engineers the most commonly used units will be those for amount of substance, mass, length, temperature and, importantly, time Property Unit Abbreviated Notation amount of substance Mole mol electric current Ampere A Length Metre m luminous intensity Candela cd Mass Kilogram kg temperature Kelvin K Time Second s Base units of measurement according to the S.I classiication he seven units within the S.I are referred to as base units, so for length that would be metre (m), but these can be converted to other systems of measurement that represent the equivalent dimension, such alternative units are referred also known as base units but not S.I., so for the example of length one could use (t) Download free eBooks at bookboon.com Chemistry for Chemical Engineers Quantifying systems Sometimes, quantities are calculated from several dimensions, this is very common in chemical engineering where lowrates, such as mass or volumetric lowrate are frequently used In this case the quantities are measured as mass/time (kg/s) and volume/time (m3/s); the corresponding units are a composition of all the dimensions involved and are known as derived units Common derived units are listed in the table below It should be noted that these dimensions have their own unit and abbreviated notation, in addition to that from their derivation Equivalent property Unit Abbreviated notation S.I derived units Volume litre l or L 0.001 m3 or 1000 cm3 Force Newton N kg m/s2 Energy kilojoule kJ 103 N m Pressure bar Bar 105 N/m2 Power kilowatt kW kJ/s Commonly used derived units Note N is deined as being equivalent to kg m/s2 because a force of N produces an acceleration of m/s2 when applied to a mass of kg It is, therefore, useful to remember that 1J 1Nm 1kg m2 s-2 in order to simplify complex units generated in some equations he base units are not always the most useful mathematical representation of the numerical value determined and may be necessary to use other methods to simplify the quantity For example, 60 s can be represented as minute (1 min), similarly 0.000001 s could be represented as 10-6 s or ms, the latter unit (microseconds) and are known as multiple units, and it is essential to be able to understand not only the quantities involved in a system but also their level of scale Chemical engineers must be comfortable with the common preixes used with S.I units and other units from around the globe Commonly used preixes are given below, with their names and numerical value Tera (T) 1012 pico (p) 10-12 Giga (G) 109 nano (n) 10-9 mega (M) 106 micro (m) 10-6 Kilo (k) 103 milli (m) 10-3 centi (c) 10-2 deci (d) 10-1 Common preixes in metric system Download free eBooks at bookboon.com Chemistry for Chemical Engineers Quantifying systems Converting units is an essential skill for all chemical engineers and the easiest method to use is fractional representation his keeps track of all numerical values and units throughout the conversion performed, allowing those units that cancel to be easily identiied he equivalence between two expressions of a given quantity may be deined in terms of a ratio (expressed here in common fraction notation): cm 10 mm centimetre per 10 millimetres Ratios of this form are called conversion factors Generally, when converting units, multiply by conversion factor(s) as fractions with new units as the numerator (top) and old units as the denominator (bottom) For example, convert 100 mm into cm: Worked example – convert the gas constant from 8.314 J mol-1 K-1 to Btu lb-mol-1 ºC-1, using the following conversions: kJ = 0.9478 Btu; kmol = 2.205 lb-mol; K = ºC Firstly, write out the value given in fractional format: 8.314 J mol K hen write out each of the required conversions in the same format, making sure that the units match and can cancel out in the working For example, if the value to be converted has J on the top line, and the conversion of kJ = 0.9478 Btu is to be applied, it is irstly required that J is converted to kJ To this, divide through by 1000 J and multiplying by kJ (as kJ = 103 J = 1000 J) Ater this, kJ is now on the top line: kJ 8.314 J kJ × = 8.314 1000 mol K mol K 1000 J It is then possible to use the conversion, kJ = 0.9478 Btu, directly, to arrive at: 8.314 0.9478 Btu kJ 0.9478 Btu × = 8.314 1000 mol K 1000 mol K kJ Download free eBooks at bookboon.com