quite
1992 中學會考預習專欄
明德出版社
3.1.Sulphur burns in air with a blue giving sulphur (IV) 'flame," oxide (SO2)
sulphur (VI)
and
oxide (503).
(19)
育教
·日二月---十年未辛曆夏
1992 中學會考預習專欄
明德出版社
MILL & DALE PRESS
Accounting (12).
Correction of Errors →→→ (1)
M. T. Kwok
Errors not affecting the agreement of the Trial Balance
In theory, if every debit entry is accompanied by a corresponding crèdit entry or entries, the two sides of a will trial
always balance
agrec. However, the agreement of the Trial. Balance doesn't mean error-free. There are still the possibilities of making mistakes and these will render our meaningless. accounting record
Therefore, it is very important for, the
us to check or recheck the entries to
detect any possible error even the trial balance 'balanced'!
Types of errors and its correction (The correction is done through Journal)
• Errors of Omission:-
This means completely omitting the transaction.
Correction:-
To restate the entries.
Example:
The purchases of goods valued $100. from Mr. Wong were completely omitted from our record.
To correct the error:-
Purchases
Mr. Wong
- Error of Commission:-
報日僑
Example:-
.Credit sales $500 to Mr. Fu were correctly entered into. The Sales Account, but entered into Mr. Yu's Account.
To correct the error:-
Str. Fü
Mr. Yu
• Error of Principle:-
五期星日七廿月二十(一九九一)年十八國民離中
經馬 日二廿
Compensating Error:-"
To correct the error:-
Ап error in debit side was compensated by an equal amount of error in credit side in a different transaction.
Dr.S
Cr.$
360*
360*
Correction:-
Dr.$ Cr.$
500
500
To restore the correct amount of entry to the accounts concerned. Example:-
Sales
Mr. Lui
insurance
expenses NAS understated by $300 where discounts received was understated by $300.
* (To reduce the two accounts to the correct level $150 since the wrong amount $510 were entered)
- Complete reversal of entries:-
This means the debit entry were
made on an account which should be credited and vice verse.
Correction:-
Correct amount is entered but in a wrong class of account (e.g. Expenses as Assets).
To correct the error:-
Insurance
Dr.$ 300
Cr.$
Correction:-
Discounts Received
300
Enter the double amount to account in order to
the
cancel
and
Dr.$ 100
Cr.$
(Same as commission),
under
error
of
restate the entries made. Example:-
• Error of Original Entry:~
100
Example:-
The amount entered is not correct.
Correction:-
Correct amount is entered but in ¿ wrong account.
Correction:-
First cancelled out the record of the wrong A/C and than restate the entry in the correct account.
3. Chemical Properties of Sulphur
chemically Sulphur 15 reactive.
A motor van is purchased at $550 by cash and it has found that the entries were made by debiting Motor Van Repairs and crediting Cash.
To correct the error:-
To enter the difference between the correct amount and the amount
A Cash purchases of $150 were made but entries were done. by debiting Cash $150 and crediting Purchases $150.
To correct the error:-
entered.
Motor Van
Dr.$ 550
cr:$
Example:-
Purchases
Cash
Motor Van Repairs
550
The Sales of $150 to Mr. Lui were entered as $510 to both sides.
END
7. Sulphites and hydrogen sulphites 7.1 Soluble sulphites and
sulphites dissociate
2-
Sulphur Taxide
Oxygen.
hydrogen give
503
Puritler
Purifier
5.4 The sulphite ion (50) has a reducing properties because it is an electron donor. On reducing other substances, It is itself. the oxidized to
sulphate ion
·50"(aq) + (0) -50 (aq)
to (aq) when dissolved in water, so, they give similar reactions as aqueous SO, solution.
7.2 Dilute strong acids liberate 50,
from metal sulphites and hydrogen- sulphites. Heating is sometimes required.
Converter packed with
a catalyst at 450*C
Unit 7: Revision notes on Sulphur and
its compounds
1. Sulphur
1. Allotropes of an element are the
different crystal forms of
the elements, ie, the different ways its constituent particles being arranged.
1.2 Solid sulphur exists in several
allotropic forms.
Solid Sulphur
S+ 02 S02
Δ
25 + 301⁄2 2503
3.2 Sulphur can combines directly with most metals and many non-metals to form the sulphides, Heating is required.
e.g.
Copper(I) sulphide (2) Conca HHORN N.B. Usually the sulphides with
metals in the lowest oxidation are obtained.
e.g. (3) H2(g) +
O.N. increases
(+4)
(+6)
50-(s)+2H (aq)
~ H2 0 (0) +502 (9)·
Examples
HSO3"(s)+H*(aq)
(1) Fe
Fes 5
Reagents
A iron(II) sulphide
(1)
Sulphate fons formed.
7.3. Boiling
with
2
2
(2) 20 + S Cu2s
@iq)+0 ̧{g} == 250,
[sq)
brown-ges! (H0,1;
2
50
(3) Halagens solution
CHO greenish-yellow to
colour loss
+2H+2C1
orange-yellow To colourless
Z +8r+H0-50 +2N +28
fight-brown to colourless
2-
.50
Or.$ 300
300
一搏殺,但有後上馬本性,如配小。
|冠四亞一季六落第,勝出來亦不算低。 | 馬乃是在下面賽程勝出。(沙田)千二~ 上陣,可謂特別矣。 一起至今共有十六次成爲首熱,戰績則是五 達、大力、張定邦及夏志信八個馬房, 從賽程方面看去,此君今季十五場頭 兩次都掄元。但卻再無另一匹謝 馬交其 ̇就中狩謝恩獒馬兩次都是剝「新紗籠」,
雄,甚至可以起「美好世界」,而有 「辣照蹺」固然可以在錦賽中爭
HEONEK E
用嚟做吓配搭。 -亦有力入腳 - 故王兆旦之馬,不妨 「馬迷之寶」亦是一匹快馬,千二
·多威」亦在狀態中,路合可配,而
其他幾匹馬亦唔錯者,如「玉」上灰勝得
三場、千四十二場、千六:一場、千八十
MILL & DALE PRESS
Chemistry (12)
H. LAM
+ C12 (9)
dized by oxidising Agents such H2SO, and conce HNO2.
O.N. increases.
Crystalline sulphur
Amorphous sulphur
3.3 Sulph
(e.g. plastic
Rhombic: Monoclinic
sulphur,
powdered
sulphur)
5 + 214504
and
sulphur. sulphur
(a-sulphur}{B-sulphur)
1.3 Differences between rhombic
monoclinic sulphur-
Im....
| Rhomble sulphur Monoctinte sulphur
Smolecules (sq)
Colour Structure
Pale-yellow
Bright yellow.
S-molecules
lass closely
packed
Density Crystal shape
(5q) closely
Higher (2.05 gem octahedral
packed
Lower (1.98 gem Handle-shaped
Stable below
Stable above 96°C
1119°C
Thermal stablilty 96°C M.P.
13°C Preparation By evaporation
fat sulphur
solution la
1.4 Rhombic sulphur
96°C www.
By slow cooling of saltan sulphur,
Monoclinic sulphur
Thus, 96°C Is known as transition temperature.
2.
Effect of heat on sulphur 2.1 Observation
Lemon-yellow °C Nobile, clear
Melts apild
amber liquid
114°C
to 190°C
Mobile, [191°C to { viscous, deep- dark-red
red liguld
Figuld
bolls
*444°C
at 445°C
Brown rapour
*2.2 Explanation
[
molecules
closely packed
in soild S
ww
113
sudden
cooling
Pleatic sulphur
melts molecules
long chains broken
up to small chains which align
rogulady
botis af 445°C
191°C
444°0
small chefna broken up.
to give Sy molecules
In vapour
separated on malting
114" to 190°C
molecules
broken up to give chains, chains
strangled and Joined up toyothar
the
350
SC12(9)
strong
as
conc.
Observations and Equations
Acidified Purple to colourless EKMAD
Jadrange to green:
22
creases
H250+ 6ND2+ 2H20
(+6)
(6)
2
50 +2F
Franclits | Yotlow to-pale-green solution
(7)
Load(19) [oxide
Black solid to White solid SO +P60 Pb50
4. Uses of sulph
(1) In manufacture
Contact Process
(2) In
. . . . .
making hydrogensulphite caso.
bleaching wood pulp in pape industry.
(3) In vulcanization of rubber (making it hard and tough).
(4) In making matches, fireworks,
gunpowder, etc.
(5) As a fungicide, insecticide and
sofl conditioners.
(6) In sulphur ointments, tablets
and drugs.
(7) In
making "hypo" (sodium thiosulphate, Na2SD3•520) -
5. Chemical Properties of 502 5.1 Dry S02 is rather inert.
SO2 becomes very reactive in the presence of water.
5.2 When dissolved in water, S02 reacts with water to form the sulphurous acid (HS03) which then ionizes to give hydronium ions (H0), the hydrogensulphite ions (HSD) and the sulphite ions (50,2“). 502{9}+H20(0)
H2503(aq)=H*{ag} _+HSQ3 ̈{aq)=2H*(aq) +50 ̧2~{
_2-(aq)
All these changes are reversible. Thus, aqueous 502 solution consists of H30*, HSO, and 50,2 tons.
2-
5.3 Sulphurous acid is a weak dibasic acid. It forms two series of salts
by neutralization: sulphites 50,2 (normal salt) and hydrogen- sulphites, HS03, (acid salt), e.g. Na, SO3, KHSO, etc.
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5.5 Aqueous 50, can bleach straw paper,
wool "and
·reduction silk by red reaction..
Thus, its bleaching effect is only temporary because the colour will be recovered due to oxidation by
+(dye
copiness
5.6 SO 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
to
burn in S02 to give white clouds of magnessium.oxide and yellow deposits of -sulphur.
SO2+ 2Mg 2Ng0 + S
O.N. decreases
(+4)
.(0)
(2) Yellow deposits of sulphur are seen when 50, reacts with HS in the presence
of 2 trace amount of water.
SO2+ 2H25 — 2H20 + 35 (+4) (~1) Oxidation, o
reduction
6. Uses of S02 (and sulphites): (1) As bleaching agent.
(2) As food preservatives. (3) As disinfectant.
(4) In manufacture of sulphuric
acid.
502
(5) In
02
Pt catalyst
H20 S03- -H2S04
purifying the
light
fractions of petroleum.
sulphur,
sodium: sulphite forms sodium thiosulphate {"hypo").
Na2503
+ S. May S
4. White precipitate is obtained on. adding baum chloride or barium tax station to some aqueous ecipitate is dissolved dilute HC) or HNO to it.
BaSO ($)+2(aq
Ba2*{aq}+\{20(e)+SO2(g)
7.5 Test for sulphite/hydrogen sulphite
If SO, is detelted on
dilute strong acid (e.g. HCT, HNO
to a solid, then the old is a metal #sulphite
hydrogen
sulphite.
Question 7.1
Dr
A gas X is evolved an arming sodium sulphite crystals with an excess of dilute hydrochloric endy The gas X 15: then
bubbledo 21cm of bromine water.
(a) Name the as X-
Write angquation of its formation. What would happen to the bromine. water?
Write an equation of the changes observed.
(c) Draw a diagram of the apparatus you would use to carry out the above experiment.
Gas X can also be obtained by heating copper turnings with some concentrated sulphuric 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 using dilute sulphuric acid and copper? Explain briefly.
A student passed an excess of gas X into 5 cm3 of 1 M sodium hydroxide
He solution.
then evaporated the resulting solution to dryness and obtained some white powder as the residue.
(g) Name the white powder obtained on evaporation. Write an equation of its formation.
When burning magnesium ribbon was put into Some gas X. the magnesium continued to burn with a spluttering flame, 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. (i) Explain the observation in the
above experiment.
(j) 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.
報日僑華
(刑明)
(HF)
Concentrated
· sulphuric ala
Absorption Tover
water
(a) Suggest a method by which sulphur
dinxide is readily obtained.
ide 15 readi
|(b) What is X? Write an equation of
its formation.
(c) What is Y? Write an equation of
its formation.
(d) Name a suitable catalyst to be put.
in the converter.
(e) Why are sulphur dioxide and oxygen
passed into the converter?
to be purified before they are
(f) Why is concentrated sulphuric acid,
but not water,
to added absorption tower?
Solution: to 0.7.1
(a) X is sulphur dioxide.
the
Na250, + 2HC1 — — NaCl + H2O + SO2
(b) The bromine water turns from yellow.
to colourless.
502 + 2H20 + Brz
(c) the set-up is shown as below,
dilute hydrochloric
test tube
godlum sulphite
Hoot
(₫) Cu + 2H2SO₫ -
21120
(e) The oxidizing power of conc.
(f) No. It is because dil H250, is not
an oxidising agent.
(g) Sodium hydrogen sulphite (NaHSO,).
50+ NaOH MaHSO
(h) The yellow solid is sulphur.
white solid is magnesium oxide. 2Mg + 50, 2Mg0+ S.
Gas X (502) does not
(1) Gas
The
not support
(se flame is
combustion, as
extinguished in it. However, the energy liberated by the burning magnesium is
great enough to decompose gas X (50) to sulphur
farm
and oxygen, so, it can continue to burn in
to the oxygen magnasium oxide. (j) The set up is:
deflagrating
spoon
gas X
ges Jor
Solution to Q.7.2
burning. magnesium
ribbon
(a) 50, is obtained by burning sulphur
in air or by roasting iron pyrite (FeS2) in air.
(b) X is sulphur trioxide,
2502(g) + O2(g) 250(9)
(c) Y is oleum,
503(9)· H2504(0) +
(d) Platinum or Vanadium(V) oxide. (e) The impurities in
or SO2 would
poison the catalyst.
(f) S03 forms misty acid fumes coming into contact with water, whereas it dissolves readily and smoothly in conc. H2504.
【養]
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H
30
兩柄緣,相當合理。 「深」爆出大後,立即轉投他稱,而:出,賽前工夫也是做得頗佳,面對自 且盛傳仍有多匹洲說馬,將於短期內他,週歲馬,仍然加工應戰,精神可嘉。 「踵而來的賽事,且低馬實力亦頗强,於此詞,期望甚深,而且自说亦高,不 图中新聞-近期特多 - 例如「手足 - 入一席第三,可說是巴有交代,今仗 過「奇錘」當日的表現,也是頗佳,走
知
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