1990-01-26 — Page 26

報日僑

五期日六月一(〇九九一年九十七國民華中 (26)

留下十分傑刻的印象。綠關;祁市場共至百 光市場時,對於該「無盡忤賣貨品低衆萬, 市政都署署長蘇耀程昨日下午參稚年

恭祝香港市民新春快樂

市署署長蘇燦祖遊花市

攤檔七百多個

#U KUI DE 12-45

設施和市,務求提高市民生话饪素。 如以很,致力提供優比的市政服務,康樂文城

******T*EXTROSE

·俄誓將至,對抗此變會怨稅香港市民 的提就亞夕日,人数政高達六萬花千人。 的人數估計均共!三十三萬 - 直在年青花東高商 KERTEBBER 47030-ZER *,校车掉設有裁剪年宵市場,亞托尼甫 蘇氏獲悉,推多利亞翁自一九六三年以

▼市民回鄉渡歲盛況今年说诚

4市政總署署長蘇燿祖昨午逛維園花市

引股具玩之市花 4

趣與感物館年新對人。

家誰落花名、法而偕待,王花桃高呎多士、

建屋數字接連下降

乍現行人止步。又見前景矇矓

算較爲便宜"

徳薩斯州一處湖★日落景色,該處價在美國可

歲波車火上爭客鄉回素

3▲買棵桃花今年行桃花運

̇况盛市花園雞晚九廿年

類廣告

個 小字卅四個

天二十元

元 各界來梅言金,每段

字如超過一價 每天收育二十元,升 四個烩含一個位、

本報分類廣舍:歡迎 大字四個,小宇光

B

個計算-長期风計

多出宇:/俦.64米品貌端载未婚

徵求

R

眞誠男友茶

古徵

產舞會 玩求

印識罠緣

26晚除夕 主學排名

1803803 有下20甸小

NARRA

7920XTNER

會

接晚,自然現境下能 號旺角彌敦道554

護清打

潔臘

1990 中學會考預習專欄

·明灕出版社 MILL & DALE PRESS

Chemistry (17).

Unit 9: Continued

6. Rate of Electrolysis

R. Chu

The rate of electrolysis depends dalaly on the rate of electron flow (the magnitude of the crent) and the rate of ion flow in the electrolyte. Thus, the rate o electrolysis will be increased by (a) using

3 larger e...

זי!

smaller resistance in thr

external circuit,

(b) placing the electrodes nearer

to each other,

a

(c) using electrodes with larger

surface area,

(d) using

水晶地板

a

More concentrated

solution of the electrolyte.

Solution

Cu) dxcited to a charge on n) deposited.

lonic charge on cu

3×(60x12) 96500

=.0.224 F

1.2.

0.03 0.02

+x

of 96 = 207

P

201 ZF

1101-

Question 9.1

2079

74

(a) Classify

substances

C.224F

ess of Pb riepos1 tex

Example 2.

0.224

How long has a current of been passed when 672 cm) of oxygen. measured at $.t.., is obtained at the anode during the electrolysis of dilute sulphuric acid?

Solution

Molar volume of gas ut sut.p. 15.

23.4 dm3.

10H - 4e-

4F [4/96500)C

· 21140

i

10001

20

0.672

0^= [4x96500; x

115800

22.4 cm3 ak s.lib.

0.672 das

et s...

the following

into

a

(a) Give brief explanation of the pink colour observed around the electrode P.

(b) lience, or otherwise, indichte which of the terminais A and B is the positive pale of the battery

(c) What is the gas collected or the

electrode Q"

Write the ionic equation

formation,

10

conductors.

(d) What

electrolytes and non-electrolytes.

A: ootassium bromide

3: sugar:

C: aqueous sulphur dioxide solution

O: graphite

E: hydrochloric acid

f: iodine crystal

ethanol ACBCH)

Hij betrachlorone hasie (CC1

1. Su phot

J: Liquid ammonia

(b)

Battery Rheos list

pl -

Duis

is the magnetude of current pissed?

Solution to 0.9.2

(a) Phoolpathalein burns pink due to the presence of the hydroxide ions [:3). The continual discharge of '(aq) ut the electrode P shifts the equilibrium H20001

*(aq) + 04 (34) to the right, thus Tera, behind an excess of "

vihica

then

ture

its

Jona

the

(e) What ould happen at the electrodo

S?

ye the ionic equation of the reaction.

(F) would there be any change the colour intensity of the copper (1) sulphate solution during the electrolysis? Explain briefly.

(g) what effect would each

the following changes have on the rate or electrolysis?

3. Using

A

smaller

current.

electric

chenciphthalein pink.

(b) 85 The positive pole.

Stripe

kelas discharged at electrode P. so, the electrode P must be the cathode and the electrode Q the

made.

(c) Chitone was.

201"(ay) —— Cl2(4) 207

(d) Molar volume of gas at 5.5.).

- 22.4 dni

ZH*

Ze

:11

1 mol

i.e.

ZF

?F

22.4dm3 at 5.t.a. 22.4cm3 at sut.3.

77.4

C = (2 x

22400

) x 96500C

·Beaker

Sedtem enlaride

Wystals

(h) If the cupper electrodes R and S

are replaced by

platinum electrodes M and N respectively,

1900

193

EX60156 0.5A

1. Placing the electrodes R and S

closer to each other.

8661115

3384

個人院

沙利道口手

370287

* 註冊西醫尘瑮·徑驗認

二、設群人、雙人厉及大

凝大,收費焱低,

租

龍九

樓短租盤

搬運 訪

電話324130 在見字速與李國泰聯

尋人啟事辦

7. Calculations on Electrolysis"

7.1 QIxt

Q is the quantity of electricity in

coulombs(0).

315 the amperes (A).

electric current

in

t is the time in seconds(s) of which the current has been passed.

7.2 A Faraday(F) denotes the quantity

of electricity carried by one mole

of electrons.

*P = 965000

OF

7.3 Faraday's First Law

Electrolysis: the mass of an element dissolved off, or liberated at,

electrode. an.

during electrolysis

15

directly proportional to the quantity of electricity passed through electrolyte.

Example: 1

the

If a current of 3A is passed for 12 min throught, fused Teadt11) bromide, what will the mass of lead ba deposited?

7.4 Faraday's

Electrolysis:

or

1100039.8 min

of

Seme

Law Second

the number of moles of the different elements dissolved off

deposited by the

Of electricity. is quantity inversely proportional to the charges on their respective ions. for example, since the charges on Cur

and Ag icos respectively are in the ratic 2:1, so, the same quantity of

would electricity deposit Cu and Ag in the mole ratio

11:2.

Example 3

Tha sama amcunt ut electricity deposits 1.905 g of copper and 1.04 at a metal. X rospectively. What is the Tonic charge on ? (A, of X is 52.)

Solution

Let X have an inmc charge of ex.

nian) depositec

1-905 0.03 mol 33.5

i. 1 the above set-up the bulb does not light up at first; however. when water is added intc the beaker, the bulb begins to light up.

(1) What are the composing

units of sodium chloride? (2) Give a brief explanation of

the observation.

i. How could you make the bulb

light up without adding water?

Question 9.2

The circuit below is for carrying out electrolysis on sodium chloride solution, using carbon electrodes, and 5 M sopper(II) sulphate solution, using copper electrodes: A few drops of phenolphthalein had been added to the sodium chloride, solution. When a steady direct, current was passed for 6 min 255, the gas collected over the electrode P occupied 22.4 cm3, measured at s.... and the solution around the electrode P Lurned pink.

SM sodium

chloride

solution

phenolphta-

By

nly) deposited =

Faraday's electrolysis, was have

1.04 52

2nd

0.02 mol

tein

Law

of

5 M copper(1)

Sulphate soluti

Rheustat Bettery

What would be discharged at the electrode N?

Give the ionic equation of the reaction.

ii. Mention

coppert11)

two

the changes of sulphate solution during the electrolysis. Expalin briefly.

Solution to 0.9.1

(a) Conductors: D.

Electrolytes: A, C, E, J. Non-electrolytes: 8, F. H, F, 1.

(b) 1. (1) Sodium chloride is composed of sodium ions (Nai and chloride ions (C1).

(2) In solid state, the ions. are not mobile, so socium chloride does not conauct electricity and the baib does not light up,

the 1. water,

icns. of sodium chloride ara dissociated and becomes mobile, 10. there is an electric current flowing and the bulb begins to light up.

ii. Heat to melt the crystals. In noten state, the ions. also mobile and conduct

become

electricity.

(e) Copper is dissolved off

electrode S.

Cu2+(aq) →→→ Cu(s) + 2e ̈

بالله

the

The (1) No.

at deposited replaced by the

arount

of

# electrode

15 Sare ambint of

cu*(aq)

C.2+ (aq) formed at the electrode S.

the

concentration of Cu2+(aq)

remains unchanged, so, there is no change in its colour intensity.

(g) i. The rate is decreased, ii. The rate is increased.

(n) 1. Oxygen gas.

401 (aq)

ii. (1) The

21120(2)+()+20

یدالله bi

of

colour Cuso lag) Fades off dae to the deposition of cu2+(50)

at electrode M.

(2) The pH of the solution decreases because the dysunarge of De ̃(aq) electrode N shifts the equilibrium H2O(2)

at

(aq) OH (29) to the right. leaving behind an excess of H(aq). So, it becomes more acidic.