UNIT CH1 - Controlling and Using Chemical Changes

Controlling and Using Chemical Changes (in order to make things, produce energy and solve environmental problems)

This unit begins with some important fundamental ideas about atoms and the use of the mole concept in calculations. Three key principles governing chemical change are then studied, viz., the position of equilibrium between reactants and products, the energy changes associated with a chemical reaction and the rate at which reactions take place. These principles are then applied to some important problems in the fields of chemical synthesis, obtaining energy and the maintenance of the environment.

Topic 1.2 - Chemical calculations

Candidates should be able to:

(a) understand the terms relative atomic mass, relative isotopic mass, relative molecular mass and molar mass, based on the 12C scale, and of the Avogadro constant, and define the mole in terms of the 12C isotope;

(b) explain the principles of the mass spectrometer and understand its uses, including the determination of the relative abundance of isotopes, relative isotopic and relative atomic masses, and describe and explain the mass spectrum of the chlorine molecule;

(c) derive empirical and molecular formulae from given data;

(d) carry out the interconversion of grams to moles (and vice-versa) for any given species;

(e) understand and use concentration data, expressed in terms of either mass or moles, per unit volume;

(f) calculate the mass of one reagent reacting with a given mass of another or forming a given mass of product(s), given the stoichiometry of the process;

(g) use the molar volume to calculate the number of moles in a given volume of a gas, at a given temperature and pressure or the volume of gas from a given number of moles;

(h) calculate the atom economy and percentage yield of a reaction using supplied data. N.B. The use of the skills listed in outcomes 1.2 (c) to (h) will be expected in all units of the AS and A2 specification.