Topic XV Analytical Chemistry
B. Topic Specific Notes
Topic Students should learn Students should be able to Notes
IV (f) Volumetric analysis involving acids and alkalis
standard solutions
acid-alkali titrations
apply the concepts of concentration of solution and use the results of acid-alkali titrations to solve stoichiometric problems
With sufficient information given, students should be able to solve problems involving back titration. (Please read the note for back titration involving aspirin on page II-7.)
V (b) Homologous series, structural formulae and naming of carbon compounds
unique nature of carbon
homologous series as illustrated by alkanes, alkenes, alkanols and alkanoic acids
structural formulae and systematic naming of alkanes, alkenes, alkanols and alkanoic acids
write structural formulae of alkanes
give systematic names of alkanes
extend the knowledge of naming carbon compounds and writing structural formulae to alkenes, alkanols and alkanoic acids
The use of different notations in drawing structural formulae of organic compounds (e.g. ) is expected.
Students should be able to give systematic names of alkanes, alkenes, alkanols and alkanoic acids with carbon chains not more than eight carbon atoms (mentioned in the overview of the topic in the Guide).
Students should be able to give systematic names for organic compounds with multiple functional groups of the same type, e.g. propane-1,2,3-triol. For other compounds with multiple functional groups, the use of order of priority of principal functional groups is not expected.2
Students should be able to give systematic names for organic compounds with unsaturated carbon-carbon bonds and/or halogen substituents, e.g. 3,3-dichloropropene and 2-bromopent-3-en-1-ol.
V (c) Alkanes and alkenes Describe the steps involved in the monosubstitution of methane with chlorine using suitable diagrams or equations
The use of suitable diagrams or chemical equations in describing the reaction steps (e.g. CH4 + Cl. CH3. + HCl) is acceptable.
II-4
Topic Students should learn Students should be able to Notes
V (d) Addition polymers understand that alkenes and unsaturated compounds can undergo addition polymerisation
Students should be reminded that the carbon-carbon double bonds in benzene and phenyl group of the aromatic compounds will not undergo addition polymerisation.
Students are not expected to explain the stability of benzene and aromatic compounds.
VI (a) Polarity of bond and molecule define the electronegativity of an atom
describe the general trends in the electronegativities of the main group elements down a group and across a period in the Periodic Table
explain how the sharing of electrons in covalent bonds leads to non-polar and polar bonds
explain the polar nature of molecules (such as HF, H2O, NH3 and CHCl3) and the non-polar nature of molecules (such as CH4 and BF3) with reference to
electronegativity, polarity of bonds and molecular shape
Dipole moment (i.e. the magnitude of the separated charge x the distance between the charges) is not expected.
Students are not expected to memorise the electronegativity scales.
But they should be able to describe the general trend in
electronegativity of elements in the Periodic Table so that they can identify the partial charges in polar molecules.
VI (b) Intermolecular forces
van der Waals’ forces
explain the existence of van der Waals’ forces in non-polar and polar covalent substances
state the factors affecting the strength of van der Waals’
forces between molecules
Classifying van der Waals’ forces into “dipole-dipole forces”,
“dispersion forces”, “permanent dipole-permanent dipole attractions”, “permanent dipole-induced dipole attractions”,
“instantaneous dipole-induced dipole attractions” etc. is not expected.3 However, students should be able to state the factors affecting the strength of van der Waals’ forces between molecules and differentiate van der Waals’ forces in non-polar and polar covalent substances.
VI (e) Shapes of simple molecules Predict and draw three-dimensional diagrams to represent shapes of (i) molecules with central atoms obeying octet rule;
and (ii) molecules with central atoms not obeying octet rule and with no lone pair of electrons (such as BF3, PCl5 and SF6)
Students are not expected to explain shapes of molecules and predict the shapes of polyatomic ions or molecules with more than one central atom.
Stating bond angles for the molecules is not expected.
3 Reference: http://goldbook.iupac.org/V06597.html
Topic Students should learn Students should be able to Notes
VII (a) Chemical cells in daily life
primary cells and secondary cells
uses of chemical cells in relation to their characteristics such as size, voltage, capacity, rechargeability and price
describe the characteristics of common primary and secondary cells:
i. zinc-carbon cell ii. alkaline manganese cell iii. silver oxide cell iv. lithium ion cell
v. nickel metal hydride (NiMH) cell vi. lead-acid accumulator
Describing structures and working principles of zinc-carbon cell, alkaline manganese cell, silver oxide cell, lithium ion cell, nickel metal hydride (NiMH) cell and lead-acid accumulator are not expected.
VII (d) Redox reactions in chemical cells
chemical cells with inert electrodes
fuel cell
With sufficient information given, students should be able to apply the concepts of electrochemistry to solve problems involving more complicated chemical cells.
VIII (a) Energy changes in chemical reactions recognise enthalpy change, H, as heat change at constant pressure
Deriving the relation between enthalpy change and heat change at constant pressure is not expected.
VIII (b) Standard enthalpy changes of reactions
carry out experimental determination of enthalpy changes using simple calorimetric method
Principle and operation procedure of a bomb calorimeter are not expected (mentioned in the overview of the topic in the Guide).
IX (a) Rate of chemical reaction
methods of following the progress of a chemical reaction
select and justify the following techniques to follow the progress of a reaction:
i. titrimetric analysis
ii. measurement of the changes in: volume / pressure of gases, mass of a mixture and colour intensity of a mixture
Calculation and instrumentation details of different techniques to follow reaction progress are not expected.
Calibration curve and related details of colorimetry are covered in
“Analytical Chemistry”.
IX (b) Factors affecting rate of reaction
concentration
temperature
surface area
catalyst
explain qualitatively the effect of changes in concentration, surface area and temperature on the rate of reaction
appreciate the importance of catalyst in chemical industries and biological systems
Maxwell-Boltzmann distribution curve in explaining the effect of changes in temperature on the rate of reaction is covered in
“Industrial Chemistry”.
Students are expected to be aware of the importance of catalyst, but not to describe specific industrial processes and biological systems (mentioned in the overview of the topic in the Guide).
II-6
Topic Students should learn Students should be able to Notes
X (c) The effect of changes in concentration and temperature on chemical equilibria
derive inductively the relation of temperature and the value of Kc from given data sets
predict qualitatively the effect of temperature on the position of equilibrium from the sign of H for the forward reaction
deduce the effect of change in concentration on the position of chemical equilibrium
Only a single homogenous reaction will be referred to when predicting changes in concentration and temperature on chemical equilibria (mentioned in the overview of the topic in the Guide).
ℓ𝓃 𝐾 = constant −ΔH
RT or log 𝐾 = constant − ΔH
2.3RT is not expected.
Details of the contact process are not expected.
Students should be able to use the reaction quotient to deduce the effect of change in concentration on the position of chemical equilibrium.
XI (a) Introduction to selected homologous series
homologous series
structural formulae and systematic naming
give systematic names, general formulae, condensed formulae and structural formulae for: alkanes, alkenes, haloalkanes, alcohols, aldehydes and ketones, carboxylic acids, esters, unsubstituted amides and primary amines
draw the structures of the compounds based on their systematic names
Students should be able to give systematic names of alkanes, alkenes, haloalkanes, alcohols, aldehydes and ketones, carboxylic acids, esters, unsubstituted amides and primary amines with carbon chains not more than eight carbon atoms (mentioned in the
overview of the topic in the Guide).
Students should be able to give systematic names for organic compounds with multiple functional groups of the same type, e.g.
propane-1,2,3-triol. For other compounds with multiple functional groups, the use of order of priority of principal functional groups is not expected.4
Students should be able to give systematic names for organic compounds with unsaturated carbon-carbon bonds and/or halogen substituents, e.g. 3,3-dichloropropene and 2-bromopent-3-en-1-ol.
4 Reference: http://www.acdlabs.com/iupac/nomenclature/93/r93_326.htm
Topic Students should learn Students should be able to Notes
XI (b) Isomerism
structural isomerism
cis-trans isomerism as exemplified by acyclic carbon compounds containing one C=C bond
enantiomerism as exemplified by compounds containing one chiral carbon
recognise the existence of cis-trans isomerism in acyclic carbon compounds resulting from restricted rotation about a C=C bond
recognise the existence of enantiomerism in compounds with only one chiral carbon
Describing and explaining properties of specific examples of cis-trans isomers such as butenedioic acid are not expected.
However, students are expected to apply their knowledge acquired in Topic VI to relate structures of cis-trans isomers to their
properties.
Students should be able to recognise that enantiomers of a chiral compound can rotate the plane of plane-polarised light by the same extent, but in opposite directions. However, details of polarimetry and concepts related to racemic mixture are not expected.
XI (c) Typical reactions of various functional groups (Annex)
describe the following reactions, in terms of reagents, reaction conditions and observations, and write the relevant chemical equations:
i. alkanes: substitution with halogens
ii. alkenes: addition of hydrogen, halogens and hydrogen halides
iii. haloalkanes: substitution with OH－(aq)
iv. alcohols: substitution with halides using hydrogen halides or phosphorus trihalides; dehydration to alkenes; oxidation of primary alcohols to aldehydes and carboxylic acids; oxidation of secondary alcohols to ketones
v. aldehydes and ketones: oxidation using Cr2O72－(aq);
reduction using LiAlH4 or NaBH4
vi. carboxylic acids: esterification and amide formation;
reduction using LiAlH4
vii. esters: hydrolysis viii. amides: hydrolysis
Reactions included are summarised in Annex.
Reactivity of haloalkanes in their substitution with hydroxide ions is not expected.
Amide formation from carboxylic acids is confined to unsubstituted amide.
For describing the substitution reactions of alcohols with halides, the use of the notations HX and PX3 as the reagents is acceptable at this level of study (X = Cl, Br or I). However, experimental details of how to produce HX and PX3 for the reactions are not expected.
XI (e) Important organic substances
structure and medical applications of acetylsalicylic acid (aspirin)
identify the functional groups of the acetylsalicylic acid molecule
recognise that aspirin is used as a drug to relieve pain, reduce inflammation and fever, and the risk of heart attack
Analysing aspirin tablets by back titration is not expected.
(Please read the note for back titration on page II-3.)
II-8
Topic Students should learn Students should be able to Notes
XIII (a) Importance of industrial processes
development of synthetic products for modern ways of living
discuss the advantages and disadvantages of using industrial processes such as petrochemistry for manufacturing products from social, economic and environmental perspectives
understand the recent progress in industrial processes such as the production of vitamin C to solve problems of inadequate or shrinking supply of natural products
Details of industrial processes of the production of vitamin C are not expected.
XIII (b) Rate equation
rate equation determined from experimental results
understand the interrelationship between reaction rate, rate constant, concentration of reactants and order of reaction
determine the rate equation of a chemical reaction by method of initial rate
Half-life of a reaction is not expected.
XIII (f) Green chemistry
principles of green chemistry
green chemistry practices
describe the relation between sustainable development and green chemistry
calculate the atom economy of a chemical reaction
relate principles of green chemistry and practices adopted in the industrial processes as exemplified by the manufacture of acetic acid (ethanoic acid)
evaluate industrial processes using principles of green chemistry
Details of industrial processes of the manufacture of acetic acid are not expected.
XIV (d) Synthetic materials in modern life
liquid crystals
describe the chemical structures and different phases of organic liquid crystals
identify the structural features of substances that exhibit liquid-crystalline behaviour
relate the uses of liquid crystals to their properties
Recall of molecular formulae of substances that exhibit liquid-crystalline behaviour is not expected.
Topic Students should learn Students should be able to Notes
XV (c) Quantitative method of analysis
volumetric analysis
gather data with appropriate instruments and apparatus in quantitative analysis
record observations and data accurately and systematically
be aware of and take necessary steps to minimise possible sources of error
perform calculations on data obtained to draw evidence-based conclusions
present observations, data, results, conclusions and sources of error either orally or in written form
justify the choice of an appropriate quantitative method for the determination of the quantity of a substance
assess possible risks associated with quantitative analysis
Details of specific chemical processes involved in volumetric analysis, other than those included in the previous topics, are not expected.
II-10
ANNEX
Reactions in Topic XI (c) Remarks
Alkane Haloalkane
X2 : Cl2, Br2
Alkene Haloalkane
X2: Cl2, Br2, I2
Alkene Alkane
Suitable catalysts: platinum (Pt), nickel (Ni) or palladium (Pd)
Alkene HX Haloalkane
HX: HF, HBr, HCl, HI Prediction of major product by Markovnikov’s Rule is required
Haloalkane Alcohol
Relative reactivity of different haloalkanes is not required
Alcohol Haloalkane
HX: HCl, HBr, HI PX3: PCl3, PBr3, PI3
Alcohol Alkene
1o Alcohol Aldehyde or Carboxylic acid
2o Alcohol Ketone
UV light, light or heat X2
H2 Pt, Ni or Pd
OH- (aq)
HX or PX3
or conc. H2SO4, heat Al2O3, heat
heat
Cr2O72-(aq) / H+(aq)
heat
Cr2O72-(aq) / H+(aq) X2 (in organic solvent)
Reactions in Topic XI (c) Remarks
Ketone or Aldehyde Alcohol
Ketone or Aldehyde Alcohol
Aldehyde Carboxylic acid
Carboxylic acid + Alcohol Ester + Water
Carboxylic acid Alcohol
Carboxylic acid Unsubstituted amide
Carboxylic acid Unsubstituted amide
Ester Carboxylate + Alcohol
Carboxylic acid
Ester Carboxylic acid + Alcohol 2. H+(aq)
1. LiAlH4, dry ether
NaBH4(aq)
heat
Cr2O72-(aq) / H+(aq)
conc. H2SO4, heat
2. H+(aq)
1. LiAlH4, dry ether
1. PCl3 2. NH3
NH3, heat
OH-(aq), heat
H+(aq)
H+(aq), heat