HKALE
Chemistry (AL)
1997 Paper I
1997
SECTION A
Answer ALL questions in this Section.
1. (a)
Write your answers in the spaces provided.
At room temperature, iron has a body-centred cubic structure.
(i) Draw the unit cell representation of iron.
(ii) Deduce the number of atoms in one unit cell of iron.
(2 marks)
(b) In a nickel-plating experiment, after passing a current of 5.0 A through an electroplating bath
containing a nickel
efficiency is 100%, deduce the oxidation state of nickel in the compound.
(3 marks)
(c)
Arrange, with explanation, the following chemical species in the order of decreasing size.
F, O and O(3 marks)
(d) Explain why
(i) the boiling point of HF is higher than that of HC1;
(ii) the boiling point of HI is higher than that of HBr.
(2 marks)
2. (a)
Consider the following dissociation reaction:
PC15(g)
PC13(g)+C12(g)
At 400 K and 101 kPa pressure, the percentage dissociation of PC1 5(g) is 86%.
(i) Calculate Kp for the reaction at 400 K.
(ii) State the effect of an increase in pressure
(I)
on Kp, and
HKALE
Chemistry (AL)
1997 Paper I
(II) On the percentage dissociation of PC15(g).
(4 marks)
(b) Account for the difference in Ka values given in the following equilibrium reaction:
H3O+(aq) + HSO4-(aq)
H2SO4(aq) + H2O( l )
Ka=7.94 X 102 mol
dm-3
HSO4-(aq) + H2O( l )
H3O+(aq) + SO42-(aq)
Ka=0.10 mol dm-3
(2 marks)
(c)
Consider the standard reduction potentials listed below:
[FeF6]3-(aq)+e-
[FeF6]4-(aq)
E
=+0.40 V
I2(aq)+2e-
2I-(aq)
E
=+0.54 V
Fe3+(aq)+e-
Fe2+(aq)
E
=+0.76V
Explain the following observations, giving a balanced equation in each case.
(i) When Fe(NO3)3(aq) is added to KI(aq), a brown solution is formed.
(ii) When concentrated KF(aq) is added to the resulting solution in (i) above, the brown
colour fades.
(4 marks)
3. (a)
For each of the following materials, identify ONE inorganic compound which is an active
ingredient:
(i) Photographic film
(ii) Gun powder
(iii) Bleaching powder
(iv) Antacid
(3 marks)
(b) For each of the following sulphur-containing chemical species, state its shape and the
oxidation state of sulphur.
HKALE
Chemistry (AL)
1997 Paper I
(i) H2S
(ii) SO2
(iii) SO42(3 marks)
(c)
The effluent from an electroplating factory contains toxic Cr2O72-(aq).
Suggest, with
balanced equations, how all
chromium-containing species can be removed from the effluent before discharge.
(4 marks)
4. (a)
The formula
HO2CCH=CHCO2H
Can represent two compounds.
(i) Draw a structure for each compound, clearly showing the difference between them.
(ii) One of the compounds reacts with P2O5(s) to give compound A.
Give the structure of A.
(2 marks)
(b) (i) Draw all possible isomeric structures of dimethylbenzene.
(ii) Upon oxidation, one of the isomers of dimethylbenzene produces a compound with the
formula C8H6O4.
This
Compound on condensation with ethane-1,2-diol gives a useful textile material B.
Give
the structure of B.
(3 marks)
(c)
(i) Give the hybridization state of the carbon atoms and the bond angles in ethene.
(ii) Outline a free radical mechanism for the conversion of ethene to poly(ethene).
Your
answer should include
Appropriate arrows to show how the new bonds are made.
(3 marks)
HKALE
Chemistry (AL)
1997 Paper I
(d) Suggest, with explanation, a chemical reaction which would enable 4-methylbenzoic acid and
4-methylphenol to be
distinguished from each other.
(2 marks)
5. (a)
Give a structure for each of the compounds D, E, F, G and H :
(1) LiAlH4
D
(i) CH3CH2CONH2
(2) H2O
Br2/NaOH(aq)
E
(ii) CH3CH2CONH2
SOCl2
F
(iii) CH3CH2CO2H
(iv) C8H16
G
(1) O3
Butanal only
(2) Zn/CH3CO2H
I2/NaOH(aq)
(v) C4H8O
H
carboxylic
acid
triiodomethane + sodium salt of a
(5 marks)
HKALE
Chemistry (AL)
1997 Paper I
(b) Consider the following reactions:
conc. H2SO4
HBr
J
K
heat
CH3CH2COC1
L
NHNH2
CH3CH2CH2OH
NO2
Na2Cr2O7
NO2
N
M
H 3O +
Give structures for J, K, L, M and N.
(5 marks)
6. (a)
(i) Vegetable oils (e.g. peanut oil) can undergo the following chemical reactions to give
useful solid products P and Q.
Excess H2/Pt
Vegetable oil
P
NaOH(aq)
Q
heat
Give one use each for P and Q.
Suggest a possible structure for P.
(ii) What is meant by the ‘iodine value’ of a fat/oil?
(3 marks)
(b) Consider the reaction:
R
C12H22O11
C6H12O6
HKALE
Chemistry (AL)
1997 Paper I
Disaccharide S
glucose only
(i) Give a chemical reagent R for the reaction.
(ii) Draw a possible structure for S, clearly showing the linkage between the monosaccharide
units.
(2 marks)
(c)
(i) Explain with the help of chemical equations, why ozone in the stratosphere is important
to life on earth.
(ii) Show, with the help of chemical equations, how the presence of chlorofluorocarbons
(CFCs) can influence the
amount of ozone in the stratosphere.
(iii) What have CFCs been widely used for in the past?
Suggest a more environmentally
acceptable chemical to
replace CFCs.
(5 marks)
END OF SECTION A
SECTION B
Answer ALL questions in this section. Write your answers in the spaces provided.
7. (a)
Briefly describe how a sample of dry chlorine gas can be prepared in the laboratory.
Draw a
labeled diagram of the
laboratory set-up and state the safety precaution(s) that is/are required.
(6 marks)
(b) An aqueous solution contained 0.40 g of a complex salt Cr(NH 3)5Cl3.
present in the solution
The free chloride ions
HKALE
Chemistry (AL)
1997 Paper I
required 21.90cm3 of 0.150 M silver nitrate(V) solution for complete precipitation.
Deduce
the structural formula
of the complex ion present in the salt.
(4 marks)
8. (a)
(i) Give the reaction conditions and the necessary chemicals/reagents required for the
formation of benzenediazonium
ion from phenylamine.
(ii) Benzenediazonium ion reacts with naphthalene-2-ol to give compound T.
Give the
structure of T.
(3 marks)
(b) You are provided with a mixture of two liquids, hexan-1-amine (U) and ethyl ethanoate (W).
Outline an experimental
procedure, based on a solvent extraction process, to enable U to be separated from W.
(3 marks)
(c)
For each of the following groups of compounds, suggest a chemical test which would enable
each compound to be
distinguished from the other(s).
In your answer also give the changes that you would expect
to observe for each
compound.
(i) CH3CH2CH2OH, (CH3)2CHOH and (CH3)3COH
(ii) C6H5CH2I and C6H5CH2C1
(4 marks)
END OF SECTION B
SECTION C
Answer ONE question only and write your answers in the AL(D) Answer Book.
HKALE
Chemistry (AL)
1997 Paper I
Marks will be allocated approximately as follows:
Chemical knowledge
50%
Organization
30%
Presentation (including proper use of English) 20%
Equations, suitable diagrams and examples are expected where appropriate.
The examiners are looking for the ability to analyse, to evaluate and to express ideas clearly.
9.
Write an essay on the variation in properties of the Group II elements and their compounds.
(20 marks)
10. Write an essay on the chemistry of amines.
(20 marks)
END OF PAPER