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.

2.2 - Energetics

Candidates should be able to:

(a) appreciate the principle of conservation of energy and construct simple energy cycles;

(b) understand that chemical reactions are accompanied by energy changes, frequently in the form of heat, and that these may be either exothermic or endothermic and depend partly on the physical states of reactants and products;

(c) define standard conditions;

(d) understand the term enthalpy change of reaction and the specific terms enthalpy change of combustion and standard molar enthalpy change of formation, . . o f H (formal definitions are not required)

(e) recall details of experimental procedures for determining enthalpy changes in aqueous solution, and calculate such enthalpy changes from experimental data using n T mc H . . = . where m and c are the mass and specific heat capacity of, for example, the water used, .T is the incremental change in temperature, and n is the number of moles;

(f) state Hess's Law and use it to calculate enthalpy changes from energy cycles;

(g) understand the concept of average bond enthalpy (energy) and use Hess's Law to carry out simple calculations involving such quantities.