AS Module 2

Foundation Physical and

Inorganic Chemistry

Introduction

This module introduces chemical energetics and kinetics. An

understanding of the factors affecting the rate of reaction is essential

in order to control rates to advantage. The position of equilibrium

can have major economic disadvantages by limiting the yield of a

given reaction. This module considers the way in which adjustment of

conditions may be used to favour a particular, desired, chemical

outcome. The methods used for the extraction of metals from natural

sources involve an understanding of the social and economic aspects

of the processes as well as an appreciation of the underlying

chemistry.

Wherever possible, candidates should carry out experimental work to

illustrate the theoretical principles included in this module.

Candidates should:

11.1 Energetics

11.1.1 Enthalpy change (DH) know that reactions can be endothermic or

exothermic.

understand that enthalpy change (DH) is the heat energy change measured under conditions of constant pressure.

know that standard enthalpy changes refer to standard conditions, i.e. 100 kPa and a stated temperature (e.g. DH298 ).

be able to recall the definition of standard enthalpy changes of combustion (DHcɵ) and formation (DHfɵ)

11.1.2 Calorimetry be able to calculate the enthalpy change from the heat

change in a reaction using the equation q = m c .T.

11.1.3 Simple applications of know Hess�s Law and be able to use it to perform

Hess�s Law simple calculations.

11.1.4 Bond enthalpies be able to determine mean bond enthalpies from given data.

be able to use mean bond enthalpies to calculate a value of DH for simple reactions.

11.2 Kinetics

11.2.1 Collision theory understand that reactions can only occur when collisions take place between particles having sufficient energy.

11.2.2 Maxwell�Boltzmann have a qualitative understanding of the Maxwell�

distribution Boltzmann distribution of molecular energies in gases.

be able to draw and interpret distribution curves for different temperatures.

11.2.3 Factors affecting reaction understand the qualitative effect of changes in

rate concentration (or pressure for gases) or surface area on

Concentration and physical the rate of reaction.

state

Temperature understand the qualitative effect of temperature changes on the rate of reaction.

be able to define the term activation energy and understand its significance.

understand that most collisions do not lead to reaction.

understand how small temperature increases can lead to a large increase in rate.

Catalysts know the meaning of the term catalyst.

understand that catalysts work by providing an alternative reaction route of lower activation energy.

11.3 Equilibria

11.3.1 The dynamic nature of know that many chemical reactions are reversible.

equilibria understand that for a reaction in equilibrium, although the

concentrations of reactants and products remain constant, both forward and reverse reactions are still proceeding.

11.3.2 Qualitative effects of be able to use Le Chatelier�s principle to predict

changes of pressure, the effects of changes in temperature, pressure

temperature and and concentration on the position of

concentration on a system equilibrium in homogeneous reactions.

in equilibrium know that a catalyst does not affect the position

of equilibrium.

11.3.3 Importance of equilibria in be able to apply these concepts to given chemical

industrial processes processes.

be able to predict qualitatively the effect of temperature on the position of equilibrium from the sign of .H for the forward reaction.

understand why a compromise temperature and pressure may be used.

11.4 Redox Reactions

11.4.1 Oxidation and reduction know that oxidation is the process of electron loss.

know that reduction is the process of electron gain.

11.4.2 Oxidation states know and be able to apply the rules for assigning oxidation states in order to work out the oxidation state of an element in a compound from its formula.

understand oxidation and reduction reactions of s and p block elements.

11.4.3 Redox equations be able to write half-equations identifying the oxidation and reduction processes in redox reactions when the reactants and products are specified.

be able to combine half-equations to give an overall redox equation.

11.5 Group VII, the Halogens

11.5.1 Trends in physical understand the trends in electronegativity and boiling

properties point of the halogens.

11.5.2 Trends in chemical understand that the ability of the halogens to oxidise

properties decreases down the group (e.g. the displacement reactions

with halide ions in aqueous solution).

11.5.3 Trends in properties of the understand the trend in reducing ability of the

halides halide ions.

know the different products formed by reaction of NaX and H2SO4.

be able to use silver nitrate solution as a test to distinguish between F-, Cl- , Br- and I- .

know the trend in solubility of the silver halides in ammonia.

11.5.4 Uses of chlorine and know the reactions of chlorine with water and the

estimation of chlorate(I) use of chlorine in water treatment.

know the reaction of chlorine with cold, dilute, aqueous NaOH and the uses of the solutions formed.

know that solutions of NaClO (e.g. bleaches) react with KI to liberate I2.

know that I2 can be estimated by titration with standard Na2S2O3 using starch indicator.

know the equations for these reactions and be able to perform calculations involving their use.

11.6 Extraction of Metals

11.6.1 Reduction of metal oxides understand how Fe is extracted by carbon

with carbon reduction at high temperature in a continuous process

from Fe 2 O 3 ; know that both C and CO are reductants in this process.

understand the use of limestone in this extraction process and the use of slag in the construction industry.

understand that Fe from the Blast Furnace is purified by the removal of C and P in a basic oxygen converter, and that S is removed by using Mg.

know that pollution problems can arise from the use of carbon as reductant and the use of sulphide ores.

understand the general limitation of carbon reduction because of carbide formation (e.g. Ti or W).

11.6.2 Reduction of metal oxides understand how Al is manufactured from purified

by electrolysis of melts bauxite (energy considerations, electrode equations and conditions only).

11.6.3 Reduction of metal halides understand how Ti is extracted from TiO2 via

with metal TiCl4 in a batch process (equations and conditions only:

either Na or Mg as a reducing agent).

understand the cost implications and hence the limited use despite the unique properties and high natural abundance of Ti.

understand that the choice of the reduction method depends upon the cost of the reductant, the energy requirements and the required purity of the metal.

 

 

11.6.4 Economic factors and understand how and why Fe and Al are recycled.

recycling know the problems associated with recycling and know

the social and economic benefits.