recall the characteristic physical (increase in melting/boiling points|decrease in electronegativity) and chemical properties of the elements of
group 7 and their compounds limited to:
the formation and properties of the
hydrogen halides - highly acidic acids - use sulphuric acid to form
identify, and make predictions from, the trends in the physical and chemical properties of the halogens and their compounds - boiling/melting points increase down (due to greater number of
electrons, hence more
van der Waals'); enthalpy hence acidity (in HX) increase down, electronegativity decreases down group (due to greater radius and electron shells), oxidising power decreases due to less attraction at edge (due to more shells)
recall uses of the halogens and their compounds - Chlorine kills bacteria in water, chlorine is in bleach, metabolism
demonstrate understanding of the terms
bond length and
bond angle: paris of electrons move as far away as possible. Non-bonding pairs stronger repulsion. Greater bond energy - smaller length
demonstrate understanding of the terms
σ-bond (line joining centres of atoms) and
π-bond (two
electron clouds on either side - asymmetric density), including the
electron density in each type
demonstrate understanding of the term
electronegativity: the power of an atom in a molecule to attract electrons to itself
select data in order to predict the nature of the structure and bonding in a given substance (
simple molecular or
giant covalent) - covalant is all non-metal; ionic is metal-non-metal; metallic is metal metal, including dative
covalency (pair of shared electrons come from one atom), bonding of intermediate type,
bond polarity (unequal sharing of electrons) and
delocalization (electrons free to move - not fixed between pair)
demonstrate understanding of the terms:
enthalpy change of atomisation (is the enthalpy change taht takes place when one mole of gaseous atoms is made from the element in its standard state under standard conditions),
enthalpy change of combustion (is the enthalpy change that takes place when one mole of a substance reacts compltely with oxygen under standard conditions, all reactants in their standard states) and
bond energy (energy required to break bond)
calculate bond energies, using
Hess’s Law (enthalpy change is independent of the route the reaction takes) and selecting appropriate data
understand that
catalysts speed up chemical reactions by providing alternative routes of lower activation energy
understand that increases of temperature speed up chemical reactions by increasing the proportion of molecules with the necessary activation energy (qualitative only)
recall that some reactions are
reversible and understand the dynamic nature of
equilibrium reactions; be able to predict the effect of a change in concentration (more on both sides), temperature (endothermic favours products) or pressure (fewer molecules) on the
position of equilibrium of a reaction (in simple qualitative cases only).
the following terms as associated with organic reactions:
homolytic (products have the same number of electrons) and
heterolytic fission(products have different numbers of electrons - forms oppositely chared ions);
free radical (highly reactive ion with unpaired),
photochemical reaction (reaction initiated by light);
chain reaction (a reaction with several sub-reactions, each product stimulating the next),
initiation (ultraviolet light homolytically fissions halogen),
propagation (free radicals form products),
termination (free radicals react to form stable products);
electrophile (an electron deficient species);
addition (more atoms than before),
substitution (same atoms) and
elimination reaction (less atoms);
hydrolysis (break down by water)
recall the typical behaviour of the alkanes and alkenes, limited to:
interpret
changes of state and the associated energy changes in terms of the particles present, their forces of attraction (intermolecular forces broken from solid->gas) and their arrangements (structural in solid - lattice, etc.)
demonstrate understanding of
van der Waals’ forces (weak forces of attraction between molecules) and
dipole-dipole interactions (electronegativities induced by electronegativity in neighbouring molecules)
interpret using the concept of van der Waals’ forces and dipole-dipole interactions:
properties which imply weak cohesive forces between all molecules (transient dipole-dipole interaction produce coheisve forces between neighbouring - due to attraction)
increase in
boiling point with increasing size among similar molecules (great size=more electrons=greater asymmetry=greater force), and with increasing surface area among isomers (more electrons in contact=greater foce)
van der Waals’ radius (half distance between nuclei of atoms in adjacent molecules) and its relationship to
atomic and
covalent radius (halfd distance between nuclei of atoms in same molecule)
demonstrate understanding of
hydrogen bonding, and identify the atoms involved in suchbonding in specified cases (One molecule must have a hydrogen atoms which is very highly positively polarised; so highly, in fact, that it is almost ready to be donated as a proton to a base. The other molecule must have one of the small strongly electronegative atoms of the elements nitrogen, oxgyen or fluorine and this atom must have available lone pair of electrons)
interpret using the concept of hydrogen bonding:
anomalous physical properties among hydrides - of the elements HCl, HBr and HI increase from one to next; HFl is highest however! HCl, etc. incrase due to van der Waals', HFl large due to hydrogen bond
anomalous physical properties among organic compounds -
demonstrate understanding of the importance of hydrogen bonding in determining the structures of some materials - used in DNA and enzymes (determin shape) - reason for shape of ice
predict some of the properties of an unfamiliar substance which contains hydrogen bonds
Topic 10
demonstrate understanding of the nomenclature and corresponding displayed and structural formulae for
halogenoalkanes: Begins with prefix "fluoro-", "chloro-", "bromo-", "iodo-" - follows normal naming conventions for organic compounds. "di-" and "tri-" prefices may be added for compounds with multiple halogens
recall the typical behaviour of halogenoalkanes, limited to:
combustion - a chlorine ion departs from the alkane
treatment with:
aqueous
alkali: chlorine atoms departs with bonding electrons
alcoholic alkali: molecule loses hydrogen and halogen
aqueous silver nitrate: No reaction if halogens are in halogenoalkane
alcoholic ammonia: two ammonia molecules will react with a halogenoalkane. One replaces the halogen - the other forms a halogen ammonium
interpret the reactions of halogenoalkanes in terms of the processes of bond-breaking and bond-making by
nucleophilic attack and by reference, as appropriate, to electron pair availability, bond polarisation and bond energy: nucleophilic attack is by a species seeking a nucleus (ie. too many electrons) - an example is alcoholic ammonium; which has a pair of unpaired electrons
recall uses of halogenoalkanes: Used as anaesthetics
demonstrate understanding of the following terms as associated with
organic reactions -
homolytic (same electrons present in products) and
hereolytic fission (different electrons in products);
free radical (uncharged species with unpaired electron),
photochemical reaction (reaction stimulated by light);
chain reaction (sequence of reactions where a reactive product causes more additional reactions);
initiation (net number of free radicals increase);
propagation (net number of free radicals stays the same);
termination (net number of free radicals decreases);
nucleophile (a species seeking positive charge) and
electrophile (a species seeking negative charge); addition (atoms in species increases), substitution (atoms in species stay the same), elimination (atoms in species decreases) and
hydrolysis reactions (reactions in which water is necessary for species breakdown).
3
Topic 11
demonstrate understanding of the terms:
rate of reaction (proceedure of reaction in terms of concentration change per time),
rate equation (rate=k[reagent] determined by slowest step),
order of reaction (rate at which reaction occurs),
rate constant (proportionality between rate and reagents),
half-life (time taken for the concentration to half),
rate-determining step (the slowest step, which causes the order to be what it is),
activation energy (minimum energy which needs to be surpassed for the reaction to proceed),
catalyst (lowers activation energy),
heterogeneous catalysis (when in different phase to reactants)
deduce from experimental data for simple zero, first and second order reactions only:
half-life - zero: half life decreases; first: half life is constant; second: half life increases
order of reaction - zero: double concentration rate remains; first: double concentration rate doubles; second: double concentration rate quadruples
rate equation - superscript number is order, add numbers together for reaction order
rate-determining step, related to possible
reaction mechanisms: slowest step, if you can vary reactants and rate remains - not in rate determining step. Rate determining step in rate equation.
activation energy (by graphical methods only; the
Arrhenius equation will be given if needed): zero: shallow/flat; first:inverse conc-time; second: steeper
comparative reactivity of the ring system with bromine and with nitric acid: more suseptible than benzene with electrophilic reagents
interpret the reactions of arenes and phenols in terms of the processes of bond-breaking and bond-making by electrophilic or nucleophilic attack and by reference, as appropriate, to electron pair availability, bond polarisation, bond energy, and the structure and bonding of the benzene ring, including links to topics 8 and 10
Topic 13
interpret the natural direction of change (
spontaneous change) as the direction of increasing number of ways of sharing energy and therefore of increasing
entropy (positive entropy change)
recall that the
entropy change in any reaction is made up of the entropy change in the system added to the entropy change in the surroundings, summarised by the expression:
recall the factors affecting the
standard entropy of a substance, in particular its
physical state (increase from solid-liquid-gas), and predict the relative entropies of different substances (qualitative only) (soft entropies are higher, complex substances are higher)
calculate the standard entropy change in the system for a stated chemical reaction using standard entropy data (∆Ssystem=∆Sproducts - ∆Sreactants
recall the expression:
∆Ssurroundings = –∆H/T
and use it to calculate entropy changes in the surroundings and, hence, calculate ∆Stotal
recall that the feasibility of a reaction depends on the balance between ∆Ssystem and ∆Ssurroundings (has to be positive overall)
Topic 14
demonstrate understanding of the term
equilibrium as applied to
physical and
chemical systems, including links to topic 7 (a reversable reaction where a dynamic balance of products and reactants is met in a closed environment)
apply the
Equilibrium Law to a chemical reaction in order to deduce the expression for the
equilibrium constants,
Kc (Kc=products/reactants) and
Kp (Kp=products/reactants), and their units
perform simple calculations related to the Equilibrium Law
predict whether a system is capable of spontaneous change, using ∆S and Kc as indicators of
thermodynamic feasibility, and the
position of equilibrium (qualitatively only) (∆S needs to be positive, Kc will give position - 1 is in middle, 0.1 favours reactants, 10 favours products)
understand and use the term:
acid (proton donor),
base (proton acceptor),
neutral (neither acid nor base),
pH (
logarithmic scale expressing hydrogen concentration),
indicator (substance which visual indicates pH),
buffer (a substance which resists change in pH)
demonstrate understanding of the term equilibrium as applied to
acid-base systems (interchange of hydrogen ions)
apply the equilibrium law to an acid-base system in order to deduce the expression for the
equilibrium constant,
Ka (Ka=products/reactants;
recall the terms
pH (= -log [H+]), Ka and
Kw (Kw = [H+] + [OH-]) and perform simple calculations using them, including calculating the pH of buffer solutions
deduce and interpret qualitatively the effect of changes in temperature and pressure on systems at equilibrium in terms of entropy changes (temperature favours products if endothermic - positive Enthalpy value; pressure favours side with fewer molecules); and the value of equilibrium constants.
Topic 15
demonstrate understanding of the nomenclature and corresponding displayed and structural formulae for
carbonyl compounds (in
aldehydes -al; and
ketones -one - ketones have a random group on the other carbon bond),
carboxylic acids (-oic acid),
esters (carbon double bonded to O; bonded to another O which is bonded to a random group - if
methyl is the random group and
butanoic acid was original - then
methyl butanoate and
acid chlorides (double bond O, single bond Cl -
ethanoyl chloride)
recall the typical behaviour of
aldehydes and
ketones limited to:
combustion:
miscibility with water: carbonyl with small
alkyl group mix readily due to hydrogen bonding due to oxygen unshared pair;
methanal totally hydrated,
ethanal down to 58%, etc.)
production from alcohols by oxidation
oxidation of aldehydes to carboxylic acids (with
dichromate(VI) ion aldehyde to carboxylic acid.
results of testing with Benedict’s solution - Aldehydes can be identified by
Benedict's reagent (ketones cannot - so are not readily oxidised)
recall the typical behaviour of carboxylic acids limited to:
solubility in water: only C1 to C4
acidity and formation of salts: weak acids in water (less than 1% ionised). Strong enough to displace
carbon dioxide from
sodium carbonate; will also neutralised
sodium hydroxide to form salt.
reaction with alcohols to form esters: due to alcohol's lone pair, warmed - acid acts as catalyst (sulphuric)
relationship to alcohols, aldehydes and ketones:
recall the typical behaviour of esters and
acyl chlorides limited to hydrolysis by water (acid or base catalyst necessary - acid removes alcohol; alkali forms an
anion (like sodium) which displaces alcohol)
interpret the reactions of carboxylic acids, aldehydes and ketones, in terms of nucleophilic or electrophilic attack, including the relative electron attracting power of the different groups in acids and their derivatives, oxidation and reduction
interpret the
infra-red spectra of acids and carbonyl compounds, including the effect of hydrogen bonding