170英文中學會考試題預習專欄
頁10第刊特年新
日四廿月一十年西己曆夏
WAH KIU YAT PC
報日僑華
一九雾气质
燒鐵 中文中學會考試題預習專欄
與文書院猛編
英文科 (九) 王淑方・
化學科
(九)
LESSON NINE
31-12-69.
CHAPTER TWO
CHEMISTRY (9)
SOLUTIONS FOR LAST WEEK
(C) DIRECT AND INDIRECT SPEECH (Continued)
NOTE: Where there is a mixture of statements and
questions the introducing verb will vary accordingly..
*•*•; (DIRECT)
John said, "I have lost my book. find it for me?"
(INDIRECT)
Can you
John said that he had lost his book and asked me if I could find it for him.
INDIRECT COMMANDS AND REQUESTS
Rules for Changing direct commands and direct re- quests into indirect ones:
(a) The introducing verb usea is not 'say' (with *
but some verb expressing command or requests such as 'order', 'command', 'ask',
'tell', or 'request", according to the shade of meani intended. -
e.g. (DIRECT)
The man said to the boy, "Go away!" (INDIRECT)
The man I'mws whe
(DIRECT)
Gaming
Joan said to Jane, "riease ring me up to-morrow."
(INDIRECT)
Joan requested Jane to ring her up the next day.
(b) A Direct Object, standing for the person orderea
is introduced.
e.g. (DIRECT)
"Come in, please," he said. INDIRECT)
He told me (him, her, etc.) to come in.
(a) The imperative form of the verb in the direct command becomes the corresponding infinitive. e.2. (DIRECT)
The teacher said, "Keep quiet!" INDIRECT)
The teacher ordered them to keep quiet,
(DIRECT)
"Sit down, boy," said the dentist. INDIRECT)
The dentist told the boy to sit dow... (a) An indirect negative command is usually ex-
pressed by 'ask', 'told', etc., and a negativ infinitive.
e.g. (DIRECT)
"Don't open the window." she said. (INDIRECT)
She told him not to open the window. (DIRECT
the teacher said.
"Don t be Lazy,'
(INDIRECT)
The teacher
not to be lazy.
EXCLAMATIONS AND WISHES
1. Assuming that the capacity of the globe, romain constant aver the range of temperatures:.
Weight of 300 c.c. air at 17°C and 740 — an
XILIR.
1740
740 x 0.3 273
I 290
760
x 1.29.
= 0.3547 .
Thus weight of 300 e.c. vapeur at 250 0 and 740
pressure
= (0.805 + 0.3547) gm.
1.1597 g.
Volume of thịạ vapeur at N.T.F. conditione
740 x 0.3 273
523
X
760
11tre
= 0.1525 litre.
Hence normal density of the vapeur
= (1.1597 + 0.1525)
7.609 g./litre
./litre
Relative density of vapour with respect te
7.609 + 0.090 = 84.55
nydrogen
2. The effect of excess concentrated sulphurio acid on the liquid C2HO ia dehydration yielding the gas C2 according to the equation:
The formula CH conforms to the lefine series of hydrocarbons of general formula CH, where
n2a. n=3. This also implies that the liquid C2 Must be an alcohol.
2
There is a possibility for twe issneric alcohola fran 09, namely n-propyl alcobel CH2.CH.CH2OH and is propyl alcohol CH2,CH(OH),CH,. However the formula C presents only one possible slefins. propylene CH, CH=CH2.
When propylene dieselves in cold sulphuric acid,... - addition reaction with H2S04 takes place. This
1
My occur in two ways:
In reporting exclamations and wishes, the Indirect speech is introduced by some verb expressing exclama- tion or wish,
e.g. (DIRECT)
They saia, "Alas: ne nave lost the match." INDIRECT)
They exclaimed that they had lost the match.
EXERCISE 10
Change the following sentences into rect Speech. (1) I said to my brother, "May I go with you?"
AWWNNER
The hunter said, "Did you see a wounded hare?"
"Is Kelly going to England?" he asked.
"Did Joan feed the dogs before sunset?" Jack asked John.
"I can't find my pencil.
Can you lend me yours?"
"Is it true that Eddy is leaving Hong Kong for
(6) America?" Edward asked his mother.
(7)
"Did they all go to the party last night?"
(7)
(8)
"Where does Ann have her hair cut?" asked Jill.
(8).
(9)
(9)
"I like Chinese food very much,"said the tourist,
(10) "I shall be reading exactly the same book next
fednesday as I am reading today, " she said. (10)
(11) "I must go to the bank before it closes," the
merchant said.
(11)
(12)"You are an excellent singer, Ann,' Bill said.
(12)
(13) "I am Chinese but I have learned English at
school," said Chan Sing.
(14) "I will take you to the cinema,. said Lilian.
(13)
(14)
(15) "I am going to swim tomorrow,
(15)
she said.
CH-CH=CH2
• CH3 + CH2 • CH2 • 0.902. OH
• CH3-CH(0.502-OH).CH2
The latter product, isopropyl hydrogen sulphate 18 the preferred product according to Markeenikerf’@ rule where hydrogen is added to the least substitut ed carbon. Hydrolysis of this hydrogen sulphate. on dilution with water and boiling, readily yielde isspropyl alcohol:
CH, CH(0.502.OH)CH + H2O
CH.CH(OH) CH + £29
Since it is said that this hydrolysis preaucr is isomeric but not identical to the original liquid, the original alcehel must be n-propyl alcohol.
These may be further verified by oxidising the wo isomers respectively with chronic acid, when n-propyl alcohol would yield propionaldehyde CH CHCHO, whilat isopropyl alcobel would yiels acetone CH,.CO.CHz •
>. THC Hиoer Procèss involves the use of the
22kcL
reversible reaction: N2 + 32 NH
being given out in the formation of 2 gm. nol. or annonia.
From the steacalumetry of the reaction, and using Avogadro's Hypothesis, as all three are gason, the volume of the product must be less than the total volume of reactants. According to Le Chater- ier'a Principle, increase of pressure will tend to drive the equilibrium from left to right. the left to right reaction is alss exsthermic, by the same principle, a better yield at equilibrium is obtainable at a low temperature.
Aa
However, in actual practice, time in LAG COOLBLY factor. The rate of chemical reaction being dependent en temperature, would require a much lenger time to reach the favorable equilibrium of Low temperatures. Hence it is more economical
KUMANDATIMELY, Te use a higher temperature and get hear a poorer equilibrium position mere quickly.
It has been found that the best conditions are 200 atmospheres pressure and 500°C. Furthermore, a catalyst is required to obtain rapid attainment of equilibrium. This being iron mixed with alumine, the latter substance serving to prevent lose of iron surface through melting and sintering at the aigh temperature of the Prece98.
Converter for catalytic oxidation of
NH3
.Pt gauze
Air
← NH2
四期星
日一月一年〇七九一屬公年九十五國民華中
In a large scale, nitric acid in prepared by
catalytic oxidation of ammonia from the exothermic
reaction: 4NH3
小
502
=. 4NO + 6H20
The process starts with liquefaction of ammonia gas under pressure, to remove any water by freezing out. The anhydroue gas is then passed together with dust-free air inte a converter. The converter contains a gauze of platinum, heated at first electrically, but later maintained at red heat wy the continuation of the exothermic reaction. Whe air-ammonia mixture is allowed to be in contact with the catalyst only momentarily, otherwise th nitric oxide formed would further decompose to nitrogen and oxygen.
From the converter, nitric oxide an mixed witn
■ørs air spontaneously giving nitrogen dioxide. This reaction, which is also exothermic may be uged in preheating the air entering the convertere;
2NO + 02
2N02
The nitrogen dioxide is then passed through baffles up a water cooled steel tower, while water] is dripping down. Nitrogen dioxide dissolves to give nitric acid and nitric oxide:
2NO2 + H2O HNO3 + HNO2
The latter being oxidised to yield more nitric acid by introducing air up the tower.
2HNO2 +0
02
2HNO
4. In chemical processes, there are two large classes of reactions that are especially of significance. Namely, acid-base reactions involving the common act of preten transfer; and oxidation- reduction reactions involving the common act of electron transfer.
HAWA Uw
Originally, the term wÄIQHPLUN WAN describe the union of one element with oxygen, but the term has been much generalised now.......... Thus for the following reactions:,
Zn +
302
ZnCl
- Zno
=
Cl2- ZnCl2 Za + 2H+(aq)
Z (aq) + Aq
regardless of whether oxygen was involvon or rou the elemental zine is converted into the same atate i.e."Zn se that all three reactions sheuzu be termed as oxidations. And oxidations should best be interpreted as a dracéas whereby elsatraum are lest.
However, for the purpose er electroneutrality there must be some way for the electrons generated. to be removed. This is effected by the presence
●f reactants capable of accepting theas electrons, 1.0. electron gain, Such a precess is termed reduction,
It can thus be seen TEST OXiartien ana FKKT GLUME. must always accompany one another in a reaction- è redex reaction. For more elegant description of the chemical state of species involved in such reactions, the concept of Oxidation States has been introduced. This being given as the différence between the atomic number and thenumber of orbital
idation.
electrons thus all elemente hase 20+ +++(ferz19),
+
state, S ", C1, Cu" (cupreus), Co Fo
are respectively -2, -1, +1, +2, and +3.
A11 reactions that bring about changes in exidation states are reasx reactions, an increase in exidation atate, is called oxidation, a decrease in exidation atate is called reduction. A substance that 'causom increase in oxidation state of another is an oxidiz- ing agent, that which causes a decrease is'a redua- ing agent.
LOS DIAL'DE
Za(s) + cu(aq):
יד
FOUEK LUxculen 18
A most romEĽNE VLO that they can be carried out with the reactants separated in space and linked only by electrical connection, e.g. galyanio cell of
= Cu(e) + Za** (aq) The overall reaction of such a cell being easily interpretable in terms of two half reactions: exidation at the zing electrode and reduction at the copper electreda,
3.
Examples of oxidation pawunapos MICE
1. Chemical addition of oxygen
232 +02 220
0 + 02 = CO2'.
2502 +02 = 303
2. Removal of hydrogen-
2H
+ O2 = 2H20 + 28
H&S + 012 ·≈ 2H01 + $
3. Addition of an aoid radical
2FeCl2 + 012 = 2FeOL
H
2FeSO4 + 302 + H2SO4 = re2(SO4)3 + 20 Examples of reduction precesses are:
1. Removal of oxygen
Cuo + z = Cu + ¤ ̧¤
Fe2O3 + 300 = 2Fe + 302
2. Addition of hydrogen
02 +225 2120 + 25 012 +
= 2H¢1 + $
3. Removal of an acid radical-
2FeCl3 + H2S = 2FGC12 + 2HCL + S
2Fe01, + Za
2FeCl2 + ZnCl2
Reversible cases of redox reactions include many examples of cell reactions as is also reduction) of Fe04 by bydrogen and oxidation of iron by
steam:
Fe3+ 4H
370 + 4H2O
QUESTIONS FOR NEXT WEEK
1. It has been determined experimentally that 1 go. of lead yielded 1.77 m. Lead oxide and 1.154 gm. lead sulphide respectively. When 1 ga. of lead)
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