波
日六廿月一十年已己曆夏
報日僑華
六期星 日三廿月二十(九八九一)年八十七國民華中( 28 )
Sulphur reactive.
is
3. Chemical Properties of Sulphur
chemically
5.4 The sulphite ion ($0.2") has
a
quite
3.1 Sulphur burns in air with a blue
oxidized to the
reducing properties because it is
Dn reducing: an electron donor. other substances, it is
sulphate
itselfi ion:
1990 中學會考預習專欄
明德出版社
flame,
giving
oxide(502)
and
oxide(50).
Sulphur (IV) sulphur(VI)
(504
1,2~).
MILL & DALE PRESS
50,
2(aq) + (0)-50
5+02
25 + 302 2503
3.2 Sulphur can combines directly with most metals and many non-metals to form the sulphides. Heating is required.
OIN. increases
(+4)
(+6)
allotropic forms.
Solid Sulphur
Crystalline
Amorphous
(4) 5(0) +
sulphran
J.
sulphur
fe.g. plastic
3.3 Sulphur
Rhombic Monoclinic
sulphur,
sulphur sulphur
powdered
(-sulphur)(-sulphur)
sulphur)
H2504 and conc. HNO3,
1.3.0ifferences between rhombic
and
is oxidized
oxidising agents such
لانا
5 + 2H2S043502 + 2H20
monoclinic sulphur:
1.1 Allotropes of an element are tne
forms of different crystal
the elements, i.e., the different ways
its constituent particles being Tarranged.
1.2 Solid sulphur exists
several
Copper (1) sulphide N.B. Usually the sulphides with the metals in the lowest oxidation
are obtained, e.y. (Cu*)¿§2ˆ‚
etc.
2.9. {3} H2{g} + S{0} ——— H2 Sig}
Chemistry (12)
R. Chu
Unit 7: Revision notes on Sulphur and
its compounds
0.9. (1) Fe + S FeS
iron(II) sulphide
(1)
Reagents 10,/AIF
with
2-
2-
1. Sulphur
(2) ZCu + S Cu2S
250
(aq)40, (g) -
· 250,
เล
7.3 Soiling
sulphur, Sodium sulphite forms sodium thiosulphate {"hypo").
its formation.
(c) What is Y?
its formation.
(2)
+ S
Na25203
ovolved
2-
ZHNO
strong
as conc.
(4)
0.N. increases
Rrobato sulphur Monocitald sulphur
(+4)
(5)
Acidified orange to green
Colour
|Bright yellow
Pale-yellow
Structure
3-malecules
S-molecules Sal
(5c) closely
backed
less closely packed
5+
·H2SO4 + 6ND2 + 2H2Q
(6)
2-
Iront Yellow to pale-green fsolution
30- +ZFe +8 504
Dansity Crystal shape
Higher
12:06 ge octahedral
Lower (1198 gem Needle-shoped
O.. increases
}
+2H
(+6)
[}}
Lead(IV) joxide
Black solid to White soild
30
P650
Examples
2-1ac)
Observations and Equations
Sulphate ions formed.
Conc. HNO, Reddish-brown yas (NO2); heat
(3)
Ha! agens
salution
2-
+heat greanish-yellow to colourless
2-
CI,+40-50
22
2 +2 +201
0: orange-yellow to
colour less
Sulphites and hydrogen sulphites
Sulphu-
Dioxida
Oxygen
and
to
hydrogen give
2-
Purifier
Purifier
.1 Soluble sulphites
sulphites dissociate
So,(aq) when dissolved in water,
so, they give similar reactions as aqueous 50, solution.
7.2 Dilute strong acids liberate S02
from metal sulphites and hydrogen- sulphites. Heating is sometimes required.
50,2 ̄(s)+24(aq)
Convert packard with
a catalyst at 450°C
Concentrated sulphuric acid
Absorption Tower
water
- H2(#)+502 (q) || (a) Suggest a method by which sulphur
dioxide is readily obtained.
·H2{2}+502(9) (b) what is X? Write an equation of
7.4 White precipitate is obtained on adding barium chloride or barium nitrate solution to some aqueous
2-
50,2. The precipitate is dissolved HNO to it."
on adding dilute HC1 or
2+
2-
1+50,
2-
+8+1,050 +2H +2Er
10: Fight-brown fo
colcur less
22
Acided Purple to calourless KMnO
2-
+2K +21
3a503(s)+2H*(aa)
Ba503(s)
Ba2+(aq)+H20{e}+5Q2(9)
7.5 Test for sulphite/hydrogen sulphite If 90 is detelted on adding a
dilute strong acid (e.g. HCL, HNO3)
hydrogen
to a solio, then the solid is a metal sulphite or sulphite.
Write an equation of
(d) Name a suitable catalyst to be pub
in the converter.
(e) Why are sulphur dioxide and oxygen to be purified before they are passed into the converter?
(f) Why is concentrated sulphuric acid,
out Fot
added water,
to the
absorption tower?
Solution to 0.7.1
(a) X is sulphur dioxide.
Na 50
=2HC1 NaCl + H2O + SO2
(b) The bromine water turns from yellow
to colourless.
+ 2HBr
50,
21120+ Brz
-H2504
(c) The set-up is shown as below.
dliute tydrochloric
acid
test tuba
sod Iuin
sulphite
Bromine
water
Hust
crystals
The mal Istability
Preparation By evaporation
X.P.
Stabia beny
96°C
Stable above 95°C
113°C
119°C
lot sulphur
By slow cooling of walten sulphur.
solution in
96 C
1.4 Rhombic
Monoclinic sulphur
95°C
Sulphur
Thus,
is known transition temperature.
2. Effect of heat on sulphur
2.1 Observation
as the
Lenon-yellow 113°C, solid
Metts
Maalie, clear
amber liguld 114°C
to
Mobite.
dark-red
營爍
Liquid
閃燦生輝誌永恆
贊誌
TAK SEK 21 2
1:91°C to
44890
1190°C viscous, deep- red liquid
sudden
bolis
at 445°C
cool Ing
Brow
Plastic
gapour,
挐恆
延
2.2 Explanation
*
O C
·00
一日千里的香港
張婉嫺(維多利亞工業中學 )
|了-一代而有著不同的表港人對祖國忘情,只
打算,也是人之常情,是在這個大時代的洪流
molecules
closely packed
in solid s
wwww
wwwwww
Sulphur
113°CAA ats molecules
separated on meiting
1910
444°C
long chains broken to small chains
which align
regulady
poils at +45°C
sa. Chains broken up
to give S molecules
in vapour
1114°C to
190°C
molecules
broken up to give chains, chains strangled and joined up together
1990 中學會考預習專欄
明德出版社
MILL & DALE PRESS
4. Uses of sulphur
(1) In manufacture
Contact Process.
(2) In
making
of H2SO4 by
calcium hydrogensulphite Ca(HS03)2 for bleaching wood industry.
paper
(3) Im vulcanizatjag be rubber
(making it hard and
(4) In making matches."fireworks.
guruwderão.
(5) Assiede insecticide and
soil conditioners.
(6) in sulpur ointments. tablets
and drugs.
(7) In making "hypa" Isodium thiosulphate, Na3203 520).
5. Chemical Properties of 502.
(5.1 Dry 50 is rather inert.
SO2 becomes very reactive in the bresence of water.
5.2 when dissolved in water 50 reacts
can bleach straw paper, reduction and silk by
5.5 Aqueous 50
wool reaction. Thus, its bleachfect is only
porary because thewatour wil be recoveredug to oxidation
H250+(dye - 0)
colourless
5.6 50 can also act as an oxidising agent when it reacts with a strong reducing agent, e.g. burning Mg, hydrogen sulphide H2S, etc.
e.g. (1) Burning Mg continues
10
burn in SC to give white clouds of magnessium oxide and yellow deposits of sulphur.
+ 2Mg →→→ 2Mg0 + `s
S02
0.N. decreases
(0)
(+4)
(2) Yellow deposits of sulphur are seen when 50 reacts
with HS in the presence
براج
with water to form the Sulphurous acid (H2503) which then fomizes give hydronium ions (
to
a water.
trace amount of
502
+
245-2420 + 35
hydrogensulphite ions (HS0," the sulphite ions (5032").
502{9}+H20(e)~K2502(aq)➡x*(aq)
•luso_*(eq)=2H*(aq)-50 0,2-(aq)
3
All these changes are reversible. Thus, aqueous $0 solution consists
2-
of Hot, H50 and 50 ions.
5.3 Sulpherous acid is a weak dibasic acid. it forms two series of salts 2-
by neutralization: sulphites 503 (normal salt) and nydrogen- Sulphites, H50, (acid salt), e.g. Na2503, kHS03, etc.
Computer (12)
K. Choy
Program debugging is an inevitable event after program coding. There are 3 main types of error:
(1) Syntax error:
It is the programming error in which the program statement is not written and presented exactly as the syntax (rule) of the language. It is the easy part of the correction. Most HKCLE questions ask questions in this style.
(2) Execution error:
6. Uses of SO, (and sulphites): (1) As bleaching agent. [2) As food preservatives. (3) As disinfectant. (4) In manufacture
acid.
of sulphuric
502
H20 503-
H2S04
(5) In
2t catalyst
purifying the fractions of petroleum.
light
Question 7.1
A gas X is evolved on warming socium sulpaite crystals with ат excess of dilute hydrochloric acid. The gas X is 2 cm3 of bromine then bubbled into water,
the gas X.
an equation of its formation.
t would happen to the bromine Water?
Write an
observed.
(c) Draw a de
would use
experiment.
the changes
the apparatus you carry out the above
Gas X can also be obed herting copper turnings with some suloburic acid.
(d) Write an equation of the reaction. (e) What property of concentrated sulphuric acid is indicated by the above reaction?
(F) Would gas X be obtained by sing dilute sulphuric acid and dopper? Explain briefly.
A student passed an excess
into 5 cm3 of 1 M sodium hydroxide
(d) Cu 2250 CuSO4 2H20 + 502 (e) The oxidizing power of conc. H2504-
(f) No. It is because dil H250, is not
an oxidising agent.
(g) Sodium hydrogen sulphite (NaHS03).
་ །
502 Näoh
NAH503
(h) The yellow solid is sulphur.
white solid is magnesium oxide.
MC SO.
2Mg0 + 5
The
(i) Gas
not X (SC2) does support-- combustion, as a candle flame is extinguished in it. However, the energy liberated by the burning magnesium S great enough to decompose gas X (502) to sulphur. and oxygen, so, it can continue to wurn in the Oxygen to form magnesium oxide.
(1) The set up is:
X
solution.
resulting
He then solution to
the
-deflagrating
and
spoon
gas X
obtained Some
white Bad as
the
residue.
gas jor
burning magnesium
ribbon
(g) Name the white" obtained on evaporationWritevan ecuation of
its format
When Caning, hestum ribbon was put into
gas X, the magnesium continued to burn with a spluttering Fame, giving a white and a yellow solid. However, if a burning candle was put into the gas X, the candle Flame was at once extinguished,
(h) what would be obtained from the
burning magnesium in gas X? Write an equation of the reaction,
the !(i) Explain
observation in the above experiment.
(1) Draw a diagram of the apparatus you would use in carrying out the above experiment.
Question 7.2
The manufacture of sulphuric acid by the Contact Process is represented by the schematic diagram below.
score more than 15 out of 25 marks. It is good that you practise 160 well for such kind of question. But on hand experience is 170 important.
Solution to 0.7.2
(a) Sg is obtained by burning sulphur nair or by roasting iron pyrite (FES)
in air.
(b) X is sulphur trioxide.
2502(g) + O2(g) → 250,(9)
(c) Y is alouc.
H2SO4(2) + 503(9)
~H 2 S2 Cz { P }
(d) Platinum or Vanadium(V) oxide.
(e) The impurities in 02 or 502 would
poison the catalyst.
(f)
503
Forms misty acid fumes coming into contact with water, whereas it dissolves readily and smoothly in conc. H2504-
PRINT "THE FIRST N TERMS OF PRINT "THE FIBONACCI SEQUENCE: “
100
REM PRINT SEQUENCE
190
200
FOR 1 TO N PRINT A
END
For such kind of questions, you only have to give the line 210 number and the corrections required. Remember not to rewrite the whole program and not to change the style of the program in order to score high mark.
Exercise
Fibonacci sequence can be generated by the addition of 2 previous consecutive terms as following.
A1
A
=.0
=1
Аз
+ A12 01 1
A1 = Ar-2 + Ap~1
where 3, 4, 5, .....
It is also the programming error that the program cannot be execute when the BASIC interpretor detects such an error. Most Connon errors include divide a number by zero and not enough A student writes the following program to find the first few terms dimension for arrays. Therefore we have to use extreme data for of the Fibonacci sequence. Study the program carefully.
program testing,
State what corrections should be made so that the program will produce the output below on the VDU. In the output, -7 and 5 are jentered through the keyboard by the user, All other items are from
the program.
[A PROGRAM TO GENERATE TERMS OF FIBONACCI SEQUENCE
HOW MANY TERMS? -7
THE NUMBER OF TERMS MUST BE AN INTEGER GREATER THAN ZERO! HOW MANY TERMS? 5
THE FIRST 5 TERMS OF THE F130NACCI SEQUENCE: 10
1
Answer:
1
Line number
2
3
Correction
10
Change to 10 PRINT "A PROGRAM TO GENERATE TERMS OF
10 WRITE "A PROGRAM TO GENERATE TERMS OF
20
Change to 20 PRINT "FIBONACCI SEQUENCE"
20
FIBONACCI SEQUENCE"
30 DIM A(N)
50
Change to 50 PRINT "HOW MANY TERMS?";
40
70
50
PRINT HOW MANY TERMS?
Change to 70 TF NO AND N = INT(N) THEN 110
60
INPUT N
90
Change to $0 GOTO 50
70
IF NO AND N INT(N) THEN 50
80
PRINT "THE NUMBER OF TERMS MUST BE AN INTEGER GREATER THAN
170
Change to 120 A(2) = 1
ZERO!"
130
Change to 130 FOR 1 - 3 TO N STEP 1
90
RETURN 50
150
REMARK GENERATION OF TERMS
Change to 150 NEXT 1
110 A(1) = 0
155
Insert line 155 PRINT
160
Change to 160 PRINT "THE FIRST N TERMS OF";
A(1) = A{I - 2) + A(L - 1) NEXT J
205
Insert line 205 NEXT I
(3) Logical error:
It is the most common error found in the algorithm of the problem. The program may or may not run. If it runs, the answer given by the program must be incorrect. Therefore testing the program must involve calculating the answer manually. Hore that one set of data are suggested so as to make Sure that no error occur for a special set of data. It is the most difficult when doing debugging. A careful and accurate 100 flowchart may be useful to avoid this type of error.
Program Correction is a compulsory question in the HKCEE.
120 A(2) = 2 130 FOR I=1 TO N STEP 2 Most 140
students can answer this question satisfactorily. Most candidates 150