1975-05-03 — Page 22

頁二第張六第日二廿月三年卯乙歷夏

登

10075:

中學會考專欄

堅慎書主編:

>>E

化學科 (廿五)。陳湛杰

CHEMISTRY (#25)

Solutions. for Chemistry (#24).

Multiple Choice Section

1. E. SV 2. D. R.T

3. PUV, 4. B. W

5. A. U

Conventional Questions

1.(a) When sulphur powder is heated gently in a test-tube, it melte at 11500 as an amber-coloured mobile Liquid. As heating continued, the colour of the liquid becomes brown, and ita viscosity increases, At about 1600, the liquid is so viscous that it cannot poured a

On further heating, the liquid be- comes almost black and somewhat

mobile again. At. 444.6°C, the molten sulphur boils and a pale yellow vapour is given off.

Originally the sulphur is -sulphur. The changes in colour and viscosity at the liquid "state are due to the appearence of two other forms, sulphur and

-sulphur. At temperatures below 160*0, more A-sulphur is present, whereas at higher temperatures no re -sulphur is present. When liquid sulphur de cooled slowly, the solid obtained is monoclinic. sulphur. When liquid-sulphur is cooled suddenly, plastic sulphur is, obtained.

(b). An element which can exist in more than one form, with the saME' chemical properties but different physical propertics is said to exhibit allotropy. Those different forma are known as allotropes; of

the :: the element. For example. element cerbon occurs in different. allotropic forms ae diamond, graphite and cake.

Sulphur existe

in several allotropes such as mono-

rhombic sulphur, sulphur, olinic:: plastic sulphur and colloidal sulphur

Preparation of monoclinic sulphus. powdered sulphur is dissolved in

hot toluene in a boiling tube. Some insulating material awh as felt.or asbestos is wrapped round the tube to lower the cooling rate. At.. above 96.50, the solution yields crystals of monoclinic alphur.

Preparation of rhombic sulphur: powdered sulphur is dissolved in carbon disulphide. After filtrat ion, the filtrate is decanted into va watch glass. As part of the: solvent evaporates, pale yellow octahedral crystals of rhombic sulphmir will be formed at below. 96.5°0.

Preparation of plastic sulphuri sulphur is heated to approach, its. boiling point and then rapidly poured into beaker of cold water. A transparent non-crystalline mass of rubber-like material is foroad.

Preparation of colloidal sulphur: when sodium thiosulphate, solution is treated with dilute hydrochloric acid, colloidal sulphur ia depostt-. ed as an amorphous white mase. :Na2S20g+2HCl→ 2H@C1+SO2↑+8%+HO

2. Sodium bicarbonate and carbonate arc.marufactured. industrially by the Solvay process.. It utilizes: the principle that sodium bicarbon- ate though soluble in water becomes much less soluble in a medium of high sodium ion concentration:

(e.g. in brine), due to the common

ion effect.

2

WAH KIU YAT PO報日僑

¡A solution of ammonium bicarbonate is first obtained by bubbling excess of carbon dioxide into a solution of ammonia; treatment of the solut- ion with brine then yields the less soluble sodium bicarbonate: h

2→ NI HCOa

2. NHq HCO3+N&.01 NH4Cl+NA(COGN Sodium carbonate is then easily prepared. from the bicarbonate by: heating:

-3"

2NaHCO → NaCO3+COS+HO↑ For the actual process, the stepa: are simultaneous, involving! a. Preparation of ammoniacal brine.

Brine is pumped. from a flooded.

salt mine to the top of a tower. It flows down through

Ammonia

mustrácam

shaped

baffle

Brinc

meny partitions whore a stream of ammonia gas is passing upward« b. Carbonation. The downward

stream of ammoniacal brine is then bubbled with carbon dioxide in a Solvay tower. Absorption of car- bon dioxide firstly formed ammonw ium carbonate and theh ammonium. bicarbonate. The reactions gener te heat and have to be cooled, by circulating water coils. A. maximum separation of sodium bi- carbonate is effected by cooling the mixture to 150. The carbon dioxide is obtained by Heating. calcium carbonate in special line

c. Filtration The solid in

filtered off, washed with water and heated to scdium carbonate. The carbon dioxide.evolved is re- turied to the reacting towers.

The

d. Recovery of aninonia. As this is.

the most costly among the raw materials, and is also theoretica-

·lly not consumedy the greatest care is taken to recover it. mother Liquor from the filters contains the ammonia as bicarbona te and chloride, The farmer is. decomposed by bubbling ateam into the solution, whilst the latter may be treated with slaked Lime from the quick lime obtained from DimeHING.

Questions for Next Week Multiple Choice Section

1. Which of the reactions listed

below is endothermic?

A. The reaction of iron with sul

phur to fom Fes

5. The reaction of sodium hydrom

xide pellete with water

0. The reaction of sodium metal

with ethanol

n. The formation of water gus

E The formation of producer gas

2. The bromide and iodide of ever.

may be distinguished in one step

by using AND

A. chlorine water

B. potassium cyanide solution

C. sodium thiosulphate solution

3. silver nitrate aplution

E concentrated, aqueous ammonit

3. Which of the following reagents

is usually stored in a rubber-

stoppered bottle?

A potassium permanganate solutior

B. ammonium hydroxide solution

C. silver nitrate solution

D. godium hydroxide solution,

E. sodium chloride solution

•Ca(OH)2+2NHC1

CaCl2+2NH ↑2H2O

The molecual weight of washing soda (Na2CO3= 10H2C} =2(23) +12+3 (16)+10(2+16)=286 Hence its equivalent weight.

286 #2 143 14

The molecular weight of baking soda

成二称个在街 山下子獅

追進個係

(NaHC0)' 2.(23)+1+12+3(36) = 64.

Hence its equivalent weight - 84 Let the fractional amount of baking soda by weight in the given dixture. be B. Thus the fractional amount of washing soda is 12.

The total equivalents in 2.34 of the given mixture is therefore

2.34(+1)

llowever, from acid-base pitmtion results, the gm. equivalents in

x

三

the mixture 30.7 0.7 0.021 Thus 2.34(+13)=0.021

1-0

and a = 0.403 and 1-2 = 0.597 Thus percentage composition of washing sode in mixture is 59.7 and that of baking soda is 40.3. 4.Which of the following compounds will react with ozone?

A. Propylene B. Hexane

C. Ethane

E. Methane

D. Cyclohexane

5. In an electrolytic celly the anode is

A the electrode at which the ions.

give up electrons

B. the electrode where reduction

takes placebo

ana

G. the negative electrode

D. the electrode at which electron enter the solution from the extemal circuit

E. the positive electrode

Conventional Questions

1. Describe clearly what chemical reactions are involved in:- (a) the change in colour, when hydrochloric acid and

13

pieces of zino are added to a. solution of ferric chloride.. (b) the formation of stalactites (e) the blue flame at the top of a

clear fire

(d) the disappearance..of the colour

:: when odorine water is exposed.

to sunlight re the hardening of mortar (f) the disappearance of the odour

when coal gia is bumed

2. A light grey powder A reacts vigorously with dilute sulphuric acid yielding a gaa B which can' extinguish a glowing splint. The gas B burns in air, but does not react with Lead acetate solution. The mixture obtained from the original reaction of A with dilute sulphuric acid contains a yellow residue.C. After filtration, the filtrate is treated with sodium hydroxide solution, when a white precipitate D, is depostied. Dis. insoluble in excess sodium hydro- xide solutioTT.

When a small amount of A is hested in a test-tube behind a nafety screenya violent reaction

The product E of was observed. this reaction reacts with dilute sulphuric acid to produce a gas P

Freacts with which barna in air.

lead acetate solution to give a

black precipitate

Determine A,B,C,D,E, and G

Discuss the chemistry of the.

reactions involved.

10975:

中學會考專櫃

堅院主編:

物理科 (廿五)·睦永熾、

Solution:

PANSICS (25)

J. (a) When the galvanometer gives a null reading, there is no current passing through it. There is no voltage drop in the internal resis-

The balance tance of cell c. length,

has the same p.d. ag that of the cello, 115v.* p.d. across the 100-cm wire is 20

P.us scross The Therefore,

x 100,

六期星 R

日三月五年五七九一歷公年四十六國民華中週一台電聞育

cli wire as 1.5v,

15om

(1) When 1-ohm resistor inserted

at:3, in

p.d. across the 100 on wire

p.d. horosa. the

1-2 x 1.00

-om wire

93.75 em

(11)

There is no eurrent flowing through the resistor, p.d. across the rem wire is stili:1.v. The balance length

75 en

(1) If the magnet (2) rests on the

shove, or the core, there is no change in lux linge in the core, No current is induced. Meter. pointer renains. at the central position.

(id). On removing the pointer, there isa change in flux linkage again. The induced current produces a polarity.

in opposing the motion of the departure of

the resting magnet (2) Meter pointer. deflects to, the

Leit.

(i) There is no magnetism on the

iron bar and the core. No current

Pointer of the mdter ie induced, remains in the central position.

(iv) On closing the switch K, magnetic flux increases. There Laa change in flue. Linkage in the coil on the Uu core. The mater pointer deflct ts

to the rignt.

There is current flowing through

the resistor.

The current is.

15

p.d. across xx

= pd. across the "ch-wire

İR 1 volt

The balance length,

-2x-100

50.cm

(b). When the magnet (23) is being placed onto the U-core, there is a change in the magnetic flux linkage in the coil, An induced current flows in the coil. The current is in such a direction as to produce magnetic poles in opposition to that of the magnet (2)

N pole on the.

left arm of

the core....

Pointar deflects

to the right.

With switch K

closed for a

few minutes,

the flux remains

'ed unaltered-

As there is no change in flux linkage in the coil, the

pointer of the

meter rêma Ing

undeflected.

時

U

On opening the switch K, the circuit broke, Flux decreases rapidly to zero. The decreas it flu.linkage: hâúnes dr.m.; the coil of the U-core, he water pointes doflects to the 1916, 〈) The directior: of defieotion

of the pointer in the gilvanometer is reversed, it the experiment in (iv) is regatted with bonnaelioan. of the inttery, rovera að,

2. (a)(1)

et. in

korte

The night line graph inlteasca Uhm saw. govenie the mailide of

urrent flowing in the restator. (2)

The amount of plate purent da vid rectly proportional to the p.1. carljed on the Date and the on tinde, Howayer, it will resol

Memionit enfinion of elections from there the Crrent w 11

temparature vises.

(1) The Jasry heate the fila sept for the mionic emission on the cathode,

(1) The folarity of this Filarant

bittery bae not affect the Sherionit ericidn t al. () If the comettiere for the

Dittery B are reytag, the

themicne il mot migrate to the *anode. The diode opposes any

carius flowing. The circuit is openal

(b) (4)

240 v

Secondary

coil.

Mimotor

coil

A ammete

( Power operating the motor.

=2.5 x 12 = Nkwatte (iii) Efficiency se mnafomer

756 Fower paxPower output

Quer at in the primary. cnil

Questars for this week

五纸

·6 galvanometer

Rh: rheostati

regulate the cur- rent in ceilx ki switch;

reversing the pelarity of tha

call.

A: ammeter

X and Y are coll? of antar of

iron wires When a currant of 1 wap in the motion of h arr. 36 6itohel on in X, the gal van oueter rails 2 divisione (to The gist. State the dire in of cu crent ir. Y and the obervation in:

() the wurrat of A in X du wit- (As) the a trant of A in % te ver (s) wan (1) is o-adjvetnd a s

to male the reading 10-A HE FAL

The current in (iii) is brough down pidly, by reducing ky to. TA (v), as in oise (1) go Za re-

placed one with wine.

of uns

(vi) ad in (i), coil is rep.sed by one with three binespas, m2 13: turns

replaced by coils with twice the

(b) A battner of end

inter resistano 2 obas 13 cör- nected in orien with a voltae efor of resistance 10 Sims and picoe ab meisteinevive 3 ohms Dhop.d across the volianeter js 3 ml (i) Calculate the em.f of the

bu te ry,

(1) Pint the power wasted in the

resistance wi

{ix}T: 0.193-g of cover is. iem-

aited fan the anthole of the ameven in 1000 Hutes what would be the valus of the ale trochemical

Equivalent of copper?.

(19) f the resistancs wire is 2%

secblometer,Wht, is its resi

tivity?

2() The guze shove a ray tube.

(i)

at a tina Duaetion of the: 尤iyoment?

(ii) Which part emite any? Should this part be made of high or lowe melting-point reals? Why?

(iii) Show how the voltage supplie

(iv). The couling systen is: 1al01.18

aa F, why is this necess%ry?

sing camera

Radioactive

Toated wit -piston

The ahove: { akaten of Wilson's Cloud Chanter med to detec pid-activity.“

(1) Give a son why the cotton be

aptured wat

(ii) Expanin why the piston is.

and then pulled, dova pushed up

nedistely?

(iii) Deterise that type of majo- activity re indicated in (I), (II) and (III) respectively.

Give

rexenas for your conclusion

期九七九第

英语去作日當变谈之用

,與以前的以文化主

之英語藝投略有出入的

皇伉儷來港

談橫縱

間之生師

·十槳,向愛好進修英「迎文學」內,共础,這出時間,每關八時

洗。「謝本以外以實

--

「會以如何鼦用術簡的

的遠衆激感新的學習力 參加播出的藝餓亦有少卅分到九點。 他方面,比方钢外的各項「無 除了担任教導工作之外。在其 助學生難悉社會,香港的歌師 目,今次討論,教師是否能協 一次公開與唐·朋友討論的現 嗨曲]節中,縱橫談其中 日循出。在星期日的「實樂交 、「縱橫談」節目,逢星期

港台特增節目

問。其中包括漆觀、

肋會來過香港。在

一次有如此之光榮,

·作四日之訪問。 希望能從中獲 在位之英皇灣臨香港 大藝華新,「勰本以外

香港開埠以來第

五月份育婭節目 有電話 跌 午宴、欣對學生表演,乘迎过米打電話來詢問間,討論,並與主持人互相研究一下的。顧機

·皇优碳會作多露之朗 外」在滿出獄間內, 導工作,在涵餘際飛對恐生關心橋段又如何?那 月四日動詞:收性目一:「本外的問題,亦換首之!致師除了在上碟時担任状 ,散後十分統,亦同時生之間能否打成一片?做迎青年朋友撥電話末 益。證去任何一個敬的意念,最簡單的,又能否協助學生解雜課本之一 的青春交响曲,由三時深至六時,其他 五

·項」,是否能協助學生獲得新

原有部份節目因而停播 被對面 有機

[「少年警訊」受蒙)

十二時的「幸盤玻璃球」,一時十五分「下午就律」中皇帝的衣飾介紹...上述節目 酆字鈞、李安求、陳惠民、歐陽美嚥、重福桓、朱培痍、與鎘、法、秦偉明。由於 別節目計有1五月九日,上午十時兒童節目「明的國王」,十一

點」, 一均屬值得市民獲悉的有族史價值之事件,畫了秦豪導,讒台組成盛海外觀,或員方面包括了:

九正之

(歡迎女岛酒會中被邀作畫挛的岛鳴) 五月七日 : 上午九時十五分到九時卅分,整法邊

『時幕酒

魏的龍

實況報導。

幸福玻璃球節目

李安求精心製作

八時,基致脊性節目的」的「課本以外」介分二 一至星期六晚七時半到一時間。今後遠星期四晚

皇女迎歡白藍

播≠青劍䓪鳴良

英女伉證來港,

【五播出,每一次節目,均有一個專題的。有訪問

爲大家糊沸的;其他由她負責的話劇節目,還有「下」的德叔》,及莫 合多個活開節目,每日中午的「風花盤製』,由一的人士,並不太多。港 在灣台播出,時間爲一小時。向由準安求主持港 能有懋會出席此一盛 ,亦有歌曲介紹。「章蕭球璃球」四月一日起,有關代表性人物出席, 在

台灣員良場(「宇山 安求養實周導的;晚上的「四人夜語·水油

李安京角實的「幸福玻環球」,遂星州一至會,邀請本港各單位的 「其中舉行一個盛大的酒

你的

少年警訊

太平山下漫步』節目

歡迎詢問交通新措施

、澱

的「眺本以外」我實性,作首次播出。江康期

·港合由黃浙之負責一節目,在五月八日開始

五月八日起推出 「課本以外」節目

三個小丈夫

的理想,不同的 - 只 樫上的差別而已。三

人生在世,都有他

共同闖天下

【 週一晚翡翠台重播

果們個程的

一一時,頂 案及實兆强兩位負責訪間的。

「奥撖女愛」,四月份開始,她更由际後走到台 聽衆烈播歌曲的。播出時間,與日中午十二時至「執導的「藍頓白慣」, 的「訪間」;同怖,亦配合當身節目的形式,爲中出現的。』由鄧炳 龍,在「宰刷玻璃球」的節目中爲你體鹳術運彩臀有對會被送昞在恐做

校隊

·桉際辯論賽仍舉行

·中學校及耕華財團日舉行,在本期

由良鳴及寫劍 兩位 「歡迎女學」的。並且 內容方面,將集中闊及平均爲大米的箭到有關方面的人士出席,接受谜案 在孔月二日八星期五)步」,由陽義禮主持。每一次的節目之中,他 逢星期一至六上午九時播出的「太平山下璨

的電話詢問,以便市民能解決有關方面之問題。

會透過兩位藝員報導一

: 這節目由撕成岁,玩家港各校隊參加,任播出,在這項目中在本星期天及下邳剃)(南大節日)時向之內,

下女扇來港之行程的。

有珠。 從「靚靚」的J]---六五一五二詢問即可。 |以接溉女皇在港四日的|述交通消息有興竪的,可於週六及下選一兩日的 ↓這個裝播劇中,你可獲觀衆電話,層篩交通之情况。有關人士,對上 上節目時間內,撥電話 - 三---三六五一五,反

「換之,在「鳖潮女岛,目中,警方交通部人員,亦會出席在節目之中答

良能沾之時 - 市面 禸交涵之措施,星期六的節

「太平山下漫步」的節目將會爲市民提供有關女

度,手法上以喝出現的。

體形式方面,較前不向,蓋子變化方面嗎?活減少了以前的「單人講述」 。當年間題,會集中煤導一下本港青年在各方面所 的警訊之外,井段有以短劃形式表現的「常年問題

的高捷的面說:星期一「社會現火讓頂短劇」,顧期二「 的對甘先,五月一日起,逢星期一百元的一般就會度」節目,在表 一個新的『青年硭務組」,除了有目前爲靑少牛歡迎

讓台電視部方面,自前由兆銘氣實鐵接滨,在五月份他有新

·考慮改意見」 四「本港施政與新建設」, 錄短片與香港有關事物」,黾期「專業人士對本 五月八日起,徐兆銘「門下」的部門,會成立 五「酇∫節目。上述五月份開始的新恩出與齊

目節視電台港 新革 大

月五

翼藝視電獎頒長署

可,做個有口的一

龍翔劇團御前演出

十大電視區及雅处典雅中,池台盧播署長主持頒獎,本港樂均合演出。 数以一種令他們容易接受的方法去海轍,會來得更收效」。在五月八日的 觀衆的。兆銘個人的意見是:「又將有意見的意見,案發炎,是賺 可以發現的是:過去一向走硬路觀的公共事務組, ,仍將會不斷的推出更多新的節目。同時,有一點 ,已開始以另一魌比較上機和一期的態度面對 的「點與角度」,「針鋒相對」,「風雅」之後

五月三日榰翔又拉像往九龍

·難關,經常在悲九上演粤劇。 浩合與市政局合辦的雅銹

龍翔樂隊參加巡遊大會 法瑞演出「主義和

* 醜嘶在女皇肪被期內,合作

來,在前方,被。行,神。西涼與伏,論功行區,共來北居切至出對戰擊侯,其夫丁山办共為西医王

山

(由社會福利署人員觀看後,與電視部負責人討論内容,及彼此交換意見。

渠够做個「小丈夫」 們的理想。他們覺得如 儷都市小孩子,亦有 洗形等。由於麼中部份內容涉及本港青少年活動間題,故在播映之先,已

- 新法,及燐女協會四圍後的拼 加件來工作,並是日嘉年華巡造大會行列中,有東撈三院,保真局 鈞劃由羅孔忠執導,並由三位童星担氣演出,計有:陳實祥、殿秋澈、招 温泉。另一項嘉年在巡遊大會-龍翔劇團中樂煉在下午香港仔畫舫巡遊,立即起返九能再次參 【文台播映;並在下星期一八五月四日)在翡翠台直播-時間爲晚上八時。【樂組方面包括:靳永業,需攝,秦森,糯,甚明。敵組方面包括-蘇漢英,雅文:陳少倫 改模成「小丈夫」一劇,于星期三(四月卅日,晚七時五十五分在麗的中 小田武術指導,盧家織音榮領導。被樂椒方面包括-畫家炮,張智,周染,羅伯婆,李斯管 虐合「獅子山下」節目最近根據不久前發生的一宗小寵離家出走的事例, 美菇演四女兵。袁日初的馬童,莫家駒的快牌。龍翔刺團,由陳惠民領導,江愨鷺舞台指導,宾 敗?抑或是小孩子本身的她?除了要將這個悌題提出來給各位:米时, 柄球演香將由袁小田演。熊民網,張炳強:李再班-張堅庭演四男兵:譚狀時,醛實雜,何兒! ▲部長?i洹應該系鼬鱼的實任?社會的制度?余漏的疏忽?學校教育的失 中人方面,樊梨花由何楚演,薛丁山由林友榮演,薛再由勞潑析沉,程咬全由吳非柔演,將由陳 ▲們相約離家,涵共所謂自由自在獨立生活了。「小丈夫」們初嘗人生的微一本將門之後,亦奉命任後術之取。据軍人強馬壯,輕微打,並將西原國之太于坐满。西凉王見大 是,在某一铎下午,他簡介:中國唐高宗時- 西馀國反叛中原,唐高宗御駕親征,對樊梨花爲征西大師。其夫薛丁山, - 該是多完美的系。於一一次御前演出,日期殓五月六日-在香港仔欣賞肪上演出。屆時,水澥演出「得勝威期」一劇。劇館 一,其子薛勇篓示鉗爲兵,一門富貴 留名千古。此劃由樊梨花,薛丁山與于藤勇殺退番將演起,

演出。

行翔森藥

有樂,包牌再藥

【翔張聯

腐粉