RI 2022 Mole Concept and Stoichiometry

Raffles Institution Year 5 H2 Chemistry 2022 Lecture Notes 1 a - The Mole Concept and Stoichiometry Content • Relative masses of atoms and molecules • The mole, the Avogadro constant • The calculation of empirical and molecular formulae • Reacting-m~sses and volumes (of solutions and gases) Learning Outcomes [The term relative formula mass or Mr will be used for ionic compounds] Candidates should be able to: (a) define the terms relative atomic, isotopic, molecular and formula masses (b) define the term mole in terms of the Avogadro constant (c) calculate the relative atomic mass of an element given the relative abundances of its isotopes (d) define the terms empirical and molecular formula (e) calculate empirical and molecular formulae, using combustion data or composition by mass (f) write and/or construct balanced equations (g) perform calculations, including use of the mole concept involving: (i) reacting masses (from formulae and equations); (ii) volumes of gases (e.g. in the burning of hydrocarbons); (iii) volumes and concentrations of solutions. [when performing calculations, candidates' answers should reflect the number of significant figures given or asked for in the question] (h) deduce stoichiometric relationships from above calculations such as those in (g) Lecture Outline References 1 Atoms and Sub-atomic Particles 1 Cambridge International AS and A Level 2 Relative Masses Chemistry (by Peter Cann and Peter Hughes) 2 Cambridge International AS and A Level 3 The Mole and Related Concepts Chemistry Coursebook with CD-ROM (by 4 Empirical and Molecular Formulae Lawrie Ryan and Roger Norris) 5 Stoichiometry 3 A Level Chemistry 4ed (by E. N. Ramsden) 4 Chemistry in Context 6ed (by Graham Hill and 6 Reacting Volumes of Gases John Holman) 7 Concentration of a Solution 5 Chemistry - The Molecular Nature of Mater 8 Acid-Base Titrations and Change (by Silberberg) 6 http:///www.chemguide.co.uk -1-

1 I Atoms and Sub-atomic Particles I _ _,___ ----__:,:_:_:_::.:..._ ________ ..__.J 1.1 The sub-atomic particles • An atom is the smallest part of an element which can ever exist, whereas a molecule is the smallest part of an element or a compound which can exist alone under ordinary conditions. • All atoms are composed of three fundamental particles - protons, neutrons and electrons. 1.2 (a} (b} (c} Sub-atomic particle proton neutron electron Symbol ;p 1n oe 0 - 1 1 Relative mass 1 1 -1840 Relative charge +1 0 -1 Location within the atom in the nucleus in the nucleus around the nucleus Important terms and definitions Term proton number or atomic number nucleon number or mass number nuclide Symbol z A Definition • The proton number (or atomic number) of an element is the number of protons in the nucleus of an atom of that element. • The atomic number determines the identity of an element. For example, every atom with an atomic number of 6 is a carbon atom; it contains 6 protons i