Pok 01 Hospital Tang Pui King Memorial College
Mock
Examination (1996 - 97)
F.7
Chemistry I
Class:
__________
Date: _____________
Name:
___________
Time allowed: 180 minutes
Class
No: ___________
(P.1 – P.13 /20)
Instructions
to students:
1. There are THREE sections in this paper. Section A, Section B and Section C.
2. ALL questions in Sections A and B are COMPULSORY. Write your answers in the spaces provided in this
Question/Answer Book.
3. Answer ONE question in Section C. Answers are to be written in the Answer Book provided.
4.
Section A carries 60 marks.
Section B carries 20 marks.
Section C carries 20 marks.
5. The total score is 100 marks.
6. A Periodic Table and some useful
constants are printed on Page 2 of this Question/ Answer
Book.
SECTION A
Answer ALL questions in this Section. Write your answers in the spaces provided.
1. (a) (i) Consider the energy cycle below for the elements of Group VII (the halogens).
(1) What does the term ΔH1 represent?
(2) What does the term ΔH2 represent?
(3) Explain why the halogen at the start of the cycle has not been given a state symbo l.
(ii)
The values of some ΔH
terms for chlorine, bromine and iodine are given in the table below.
|
|
Cl |
Br |
I |
|
Hf/kJ
mol-1 |
121 |
112 |
107 |
|
He/kJmol-1 |
-364 |
-342 |
-295 |
|
Hhvd/kJ
mol-1 |
-381 |
-351 |
-307 |
(1) Calculate ΔH2
for each of the halogens.
(2) What do these values indicate?
(7 marks)
(b)
An important commercial process is the electrolysis of brine using inert
electrodes.
(i)
Give ion-electron equations, with state symbols, for the electrode
reactions:
(1)
at the cathode,
(2)
at the anode.
(ii)
When the
electrolytic cell is stirred, two of the products react to form a solution.
Write
an equation for the reaction which occurs if the cell is kept cold.
(iii)
State two everyday uses of the solution formed in (ii)
(3 marks)
2. (a) It is found that, if one mole of ethanoic acid and
0.5 moles of ethanol react to
equilibrium at a certain temperature, 0.423 moles of ethyl
ethanoate are produced.
(i)
Calculate Kc
(ii) Calculate the composition of the equilibrium mixture obtained if 3 moles of ethanoic acid, 5 moles
of ethanol and 2
moles of water were allowed to react to equilibrium.
(5 marks)
(b) (i) In the first long period of the periodic table, the element from Sc (Z = 21) to Zn (Z = 30) are said to
belong to the d-block. Some but not all of these elements are "transition elements".
(1)
What is meant by d-block element?
(2)
What is meant by transition element?
(3) Which of the element(s) mentioned is/are in the d-block but are not transition element(s)?
(ii) In the spaces below, insert the electronic configurations of the atoms and ions shown.
(5 marks)
3. (a) (i) Complete
the following equations by filling in me three boxes.
(ii)
Give one use of Gamma radiation.
(2 marks)
(b) Give the functions for the following compartments of a mass
spectrometer:
(i) ionization chamber
(ii) magnetic field
(2 marks)
(c)
The diagram below shows an apparatus in which ammonia reacts with an excess of
hot copper (II) oxide.
(i) What are
(1)
the liquid L and
(2)
the gas G?
(ii) Write down the equation for the reaction.
(iii) What does this reaction tell about the nature of
ammonia?
(iv) What is the function of
(1) the glass wool,
(2) the mixture of ice and salt?
(v) Explain why dry ammonia gas is used to enter the tube.
(vi) Although the ammonia gas is in excess, the gas collected in the gas jar does not contain ammonia. Explain
why this is so?
(vii) Describe what
can you observe to the copper (II) oxide in the combustion tube after the
reaction.
(viii) What will be the pH of liquid L? Explain your answer.
(6 marks)
4. (a) The co-ordination number of each central metal ion is given below, write down the formulae and names of
the complex ions formed between :
(ii) Fe3+ and CN-,
(co-ordination number =6)
(iii) Co2+ and Cl-,
(co-ordination
number = 4)
(iv) Fe2+ and H2O.
(co-ordination number = 6)
(4
marks)
(b) A compound X, containing only carbon, hydrogen and oxygen, contains C, 62.07% and H, 10.34%. It
was also found that the volume occupied by 2 g of vapour X is 1.415 dm3 at 1 atm and 227°C. (Given 1
atm = 1.013 x 105 Nm-2)
Find
(i) the empirical formula of X, and
(ii) the
molecular formula of X.
(6 marks)
5.
(a) Butenedioic acid has two geometric isomers, both of them are solids at
room temperature.
(i) Describe a physical test which would enable you to distinguish between
them and explain briefly.
(ii) Describe a chemical test which would enable you to distinguish between
them and explain briefly.
(4
marks)
(b) (i) Does ethanoyl chloride CHaCOCl react more or less vigorously than chloroethane C2H5Cl, in its
reactions with the nucleophilic reagent -- water ?
(ii) Explain the differences in reactivity between acid halide and alkyl halide by considering the charge on
the carbon atom in the COCl and CCl group in (i).
(3 marks)
(c) Ethanoic acid is a stronger acid than ethanol. Why ?
(3
marks)
6.
(a) The compound 2-hydroxypropanoic acid may be formed as shown in the
following reaction scheme.
CH3CHO---HCN---> CH3CH(OH)CN ---hydrolysis--->
CH3CH(OH)COOH
(i) 2-hydroxypropanoic acid can exist as two optically active isomers. Draw
their structural formulae.
(ii) When using the pathway suggested, a 'racemic mixture'
will be formed.
Explain.
(4
marks)
(b) Developed countries once made wide use of chlorofluorocarbons (CFCs) but recently they have agreed
to ban the use of CFCs by the end of this century.
(i)
State TWO major uses of 'freons' (chlorofluorocarbons, CFCs).
(ii) What properties of freons make them useful to perform
the jobs in (i) ?
(iii) Even though CFCs are useful chemicals, they have been banned by many
developed countries. Why?
(3 marks)
(c) (i) Give THREE
conditions are necessary for combustion.
(ii) Give THREE reasons why bromochlorofluoromethane (BCF) can be used for extinguishing fires caused
by electrical faults.
END OF SECION A
SECTION B
COMPULSORY
questions. Write your answers in the spaces provided.
7. (a) Seven students to determine the boiling temperature of propan-1-ol using similar sets of apparatus,
reported values
in degrees Celsius, of 96.4, 97.0, 97.1, 97.1, 97.2, 97.3 and 97.7
respectively.
(i) Suggest what might have caused the discrepancies in the boiling
temperature readings.
(ii) Write down those boiling temperature readings which you would not use to calculate the mean boiling
temperature of propan-1-ol.
(iii) Calculate the mean boiling temperature
in 2 decimal places.
(3 marks)
(b) Group I and II elements show characteristic flame test.
(i)
Describe how to carry out flame test.
(ii) What is the flame colour of barium?
(iii) How to detect the flame colour of sodium and potassium in a mixture of
KC1 and NaCl?
(5 marks)
(c) A small protein containing the five amino acids A to E was broken down, using acid, to give a solution
containing the free amino acids. A two-dimensional chromatogram was then run on the resulting solution,
using the two solvents as shown in the diagram. The origin is marked in the diagram with a cross. After
developing, the spots obtained were as shown
on the diagram.
(i) Draw the expected arrangement of amino acids for the above mixture after using only solvent 2. Label the
position A to E on the diagram.
(ii) Explain why two solvent mixtures are used in the
experiment.
8. Sodium ethanedioate (oxalate) can be used as a primary standard in an experiment to determine the
percentage of iron in a sample of iron wire. The iron wire is first converted to iron(II) sulphate and then
titrated against a standard potassium manganate (VII) solution.
(a)
What is meant by a primary standard?
(b) Describe the experimental procedure required to
(i) Standardize the potassium manganate (VII) solution.
(ii) prepare the iron(II) solution from the iron wire.
(iii) State the product(s) formed from the ethanedioate ion after reaction
with manganate(VII).
(10
marks)
END
O
F SECTION B
SECTION C
Answer ONE
question only and write your answers in the Answer Book.
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. Chemical equilibrium is important in any industrial process. Using Haber Process as example, discuss the
factors that will affect an equilibrium.
(20 marks)
10.
Write an essay to discuss the Air Pollution.
You should describe the major air pollutants and their sources and give the effects of polluted air on the
environment. Besides, the physical method, chemical method and incineration in the treatment of chemical
waste from industry and laboratories should be
mentioned.
(20 marks)
END
OF PAPER
Pok 01 Hospital Tang
Pui King Memorial College
Mock Examination (1996
- 97)
F.7 Chemistry II
Class:
___________
Date: ___________
Name:
________________
Time allowed: 180 minutes
Class No:
__________
(P.1 – P. 10 / 20)
Instructions
to students:
1.
There are TWO sections in this paper, Section A and Section B.
2.
Answer THREE questions in Section A.
3.
Answer TWO questions in Section B.
4.
All questions carry equal marks.
5.
Answers to questions in Section A and B are to be written in the Answer Book.
6. Section A carries 60 marks.
Section B carries 40
marks.
7.
The total score is 100 marks.
8. A periodic Table and some useful constants are printed on page 10 of these question
papers.
SECTION A
Answer any THREE questions in this Section
1. (a)
Apple juice has a pH of 3.5.
(i)
Define pH.
(ii)
Calculate the molar concentration of hydrogen ions in apple juice.
Apple juice can be titrated with standard alkali. A 25.0 cm3 sample of apple juice was exactly neutralized
by
27.5 cm3 of 0.10 mol dm-1 sodium hydroxide using
phenolphthalein as indicator.
(iii) Assuming that apple juice contains a single acid which is monobasic, calculate the molar concentration of the acid in the juice.
(iv)
(1) How can you explain the difference between the two results you have
obtained in (ii) and (iii)?
(2) What constant can be determined from these two results?
(3) Calculate a numerical value of this constant.
(v)
Suggest two reasons why phenolphthalein is a suitable indicator for this
titration.
(b) The phase diagram of carbon
dioxide is shown below:
Answer the following questions
by using this phase diagram.
(i)
What do you understand by the following
(1)
regions I, II and III.
(2)
point T
(ii)
Explain the fact that solid carbon dioxide used for packing ice cream does not
melt to form liquid carbon dioxide.
(iii)
Give the conditions under which liquid carbon dioxide can be obtained?
(6
marks)
(c) (i)
Explain me fact that both ch4
and NH3 have shapes based on the tetrahedron.
(ii)
Deduce the shape of BCl3.
(iii)
Draw the molecular shapes of
(1)
PCl5(g)
(2)
SF4(g)
(5 marks)
2.
(a) (i) Explain why blocks of magnesium are often strapped to the steel hulls
of ocean-going ships.
(ii)
(1) Describe the electrochemical processes that take place during the rusting
of iron. Illustrate your answer with relevant half-equations.
(2)
State two conditions that cause iron to rust more quickly.
(5
marks)
(b) Given the standard electrode potentials at 298k for the following
electrodes:
Cu2+ (aq)/ Cu (s)
+0.34V
Ag+ (aq)/ Ag (s)
+0.80V
Zn2+ (aq)/ Zn (s)
+0.760V
(i)
Draw cell diagrams for
(1)
a copper-silver cell and
(2)
a copper-zinc cel
Give
the positive and negative poles for each cell, using IUPAC convention.
(ii)
Give the overall cell reactions for the cells in (i) and calculate their
standard e.m.fs. at 298K.
(6 marks)
(c) (i)(l) What is meant by the term partition coefficient?
(2) Under what circumstances does a partition coefficient vary?
(ii) Under certain conditions, the partition coefficient of a substance X between methylbenzene and water is
12. X being
more soluble in methylbenzene than water.
(1) What mass of X will be extracted from 200 cm3 of an aqueous solution containing 8g of X by
shaking
it with 50 cm3 of methylbenzene?
(2) What mass of X would have been extracted from the 200 cm3 of aqueous solution containing 8 g
of X by shaking successively with two
separate 25 cm3 portions of methylbenzene?
(3) Compare the total mass of X extracted in these two successive extractions with that obtained from
a single extraction using 50 cm3 of methylbenzene. Comment on the difference.
(9 marks)
3. (a) This question concerns an investigation into the acid-catalysed iodination of propanone which was carried
out
as follows.
I. 50 cm3 of a 1 M solution of propanone was added quickly with stirring to a flask containing 25 cm3 of
0.02 M iodine solution and 25 cm3
of 1 M acid. A clock was started at the moment of addition.
II. A 10 cm3 portion was withdrawn from the above reaction mixture, using a pipette, and run into a flask
containing sodium hydrogencarbonate solution. The time was noted when half the 10 cm3 portion had
been added. This mixture was then titrated
with standard sodium thiosulphate solution.
III. Further 10 cm3 portions were withdrawn at approximately 10 minute intervals from the reaction mixture
and the procedure in II repeated.
sodium thiosulphate.
(ii)
Explain why the experiment used a large excess of propanone.
(iii)
What did the volume of the sodium thiosulphate solution in the
titration indicate?
(iv) A graph of volume of sodium thiosulphate against time was plotted. A straight line was obtained.
What
was the best deduction from this graph?
(4
marks)
(b) The rate constant, k, varies with temperature, T, according to the
Arrhenius equation
k = Ae-E/RT
where
A and R are constants and E is the activation energy
(i) Calculate the
Arrhenius activation energy for the decomposition of N2O5
from the following data:
at 35°C
k = 6.60 x 10-5s-1, and
at 65°C
k = 2.40 x 10-3 s-1
(ii) What
is the physical meaning of A in the Arrhenius equation?
(4 marks)
(c) The atomic radii and first ionization enthalpies of seven elements
in a period of the Periodic Table are given in the following table:
|
|
Na |
Mg |
Al |
Si |
P |
S |
C1 |
|
Atomic radius (nm) |
0.156 |
0.136 |
0.125 |
0.117 |
0.110 |
0.104 |
0.099 |
|
First ionization
enthalpy (kJ mol-1) |
492 |
743 |
579 |
791 |
1061 |
1003 |
1254 |
(i) Why does atomic radius decrease across the Periodic
Table?
(ii) Explain why there
is a general trend in the first ionization enthalpy and suggest explanation
for each of the discrepancies in the trend.
(6
marks)
(d) Compare the general features between d-blocks and s-block Metals.
(6 marks)
4.
(a) Sulphur and concentrated nitric acid are heated together in tube X. After
some time brown fumes appear in tube X. The diagram of the apparatus is shown
below:
(i)
Give the name of me brown fumes.
(ii)
Explain how me brown fumes are formed. Write an equation for the
reaction that occurs in tube X.
(iii)
Brown fumes do not appear in tube Y. Explain.
(iv)
What would be observed in tube Z? Explain your answer.
(v) At the end of the experiment, the solution in tube Y is found to conduct electricity better than the
water which is originally present. Explain
what there is a change in conductivity.
(8
marks)
(b) Consider the reaction between chlorine and water:
Cl2
(g) + H2O (l) ————> HClO (aq) + HCl (aq)
(i) Explain the meaning of the term 'disproportionation' using the above reaction as an example.
(ii) Would you classify the reaction between fluorine and water as disproportionation reaction?
Explain your answer.
